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zfs/man/man5/zfs-module-parameters.5

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Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
'\" te
.\" Copyright (c) 2013 by Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
Reference_tracking_enable should be a module param To make use of zfs_refcount_held tunable it should be a module parameter in open-zfs. Also, since the macros will auto-generate OS specific tunables, removed the existing zfs_refcount_held reference in module/os/freebsd/zfs/sysctl_os.c. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Allan Jude <allan@klarasystems.com> Signed-off-by: Don Brady <don.brady@delphix.com> Closes #11753
2021-03-16 21:56:17 +00:00
.\" Copyright (c) 2019, 2021 by Delphix. All rights reserved.
Freeing throttle should account for holes Deletion throttle currently does not account for holes in a file. This means that it can activate when it shouldn't. To fix it we switch the throttle to be based on the number of L1 blocks we will have to dirty when freeing Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> Closes #7725 Closes #7888
2019-02-12 20:01:08 +00:00
.\" Copyright (c) 2019 Datto Inc.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.\" The contents of this file are subject to the terms of the Common Development
.\" and Distribution License (the "License"). You may not use this file except
.\" in compliance with the License. You can obtain a copy of the license at
.\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
.\"
.\" See the License for the specific language governing permissions and
.\" limitations under the License. When distributing Covered Code, include this
.\" CDDL HEADER in each file and include the License file at
.\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this
.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
.\" own identifying information:
.\" Portions Copyright [yyyy] [name of copyright owner]
Don't scale zfs_zevent_len_max by CPU count The lower bound for this scaling to too low and the upper bound is too high. Use a fixed default length of 512 instead, which is a reasonable value on any system. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #11822
2021-03-31 17:56:37 +00:00
.TH ZFS-MODULE-PARAMETERS 5 "Mar 31, 2021" OpenZFS
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.SH NAME
zfs\-module\-parameters \- ZFS module parameters
.SH DESCRIPTION
.sp
.LP
Description of the different parameters to the ZFS module.
.SS "Module parameters"
.sp
.LP
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 17:52:48 +00:00
.sp
.ne 2
.na
\fBdbuf_cache_max_bytes\fR (ulong)
.ad
.RS 12n
Limit dbuf cache sizes based only on ARC target size by default Set the initial max sizes to ULONG_MAX to allow the caches to grow with the ARC. Recalculate the metadata cache size on demand so it can adapt, too. Update descriptions in zfs-module-parameters(5). Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <matt@delphix.com> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10563 Closes #10610
2020-07-25 03:38:48 +00:00
Maximum size in bytes of the dbuf cache. The target size is determined by the
MIN versus \fB1/2^dbuf_cache_shift\fR (1/32) of the target ARC size. The
behavior of the dbuf cache and its associated settings can be observed via the
\fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 17:52:48 +00:00
.sp
Limit dbuf cache sizes based only on ARC target size by default Set the initial max sizes to ULONG_MAX to allow the caches to grow with the ARC. Recalculate the metadata cache size on demand so it can adapt, too. Update descriptions in zfs-module-parameters(5). Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <matt@delphix.com> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10563 Closes #10610
2020-07-25 03:38:48 +00:00
Default value: \fBULONG_MAX\fR.
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 17:52:48 +00:00
.RE
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 17:49:50 +00:00
.sp
.ne 2
.na
\fBdbuf_metadata_cache_max_bytes\fR (ulong)
.ad
.RS 12n
Limit dbuf cache sizes based only on ARC target size by default Set the initial max sizes to ULONG_MAX to allow the caches to grow with the ARC. Recalculate the metadata cache size on demand so it can adapt, too. Update descriptions in zfs-module-parameters(5). Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <matt@delphix.com> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10563 Closes #10610
2020-07-25 03:38:48 +00:00
Maximum size in bytes of the metadata dbuf cache. The target size is
determined by the MIN versus \fB1/2^dbuf_metadata_cache_shift\fR (1/64) of the
target ARC size. The behavior of the metadata dbuf cache and its associated
settings can be observed via the \fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 17:49:50 +00:00
.sp
Limit dbuf cache sizes based only on ARC target size by default Set the initial max sizes to ULONG_MAX to allow the caches to grow with the ARC. Recalculate the metadata cache size on demand so it can adapt, too. Update descriptions in zfs-module-parameters(5). Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <matt@delphix.com> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10563 Closes #10610
2020-07-25 03:38:48 +00:00
Default value: \fBULONG_MAX\fR.
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 17:49:50 +00:00
.RE
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 17:52:48 +00:00
.sp
.ne 2
.na
\fBdbuf_cache_hiwater_pct\fR (uint)
.ad
.RS 12n
The percentage over \fBdbuf_cache_max_bytes\fR when dbufs must be evicted
directly.
.sp
Default value: \fB10\fR%.
.RE
.sp
.ne 2
.na
\fBdbuf_cache_lowater_pct\fR (uint)
.ad
.RS 12n
The percentage below \fBdbuf_cache_max_bytes\fR when the evict thread stops
evicting dbufs.
.sp
Default value: \fB10\fR%.
.RE
.sp
.ne 2
.na
\fBdbuf_cache_shift\fR (int)
.ad
.RS 12n
Set the size of the dbuf cache, \fBdbuf_cache_max_bytes\fR, to a log2 fraction
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
of the target ARC size.
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 17:52:48 +00:00
.sp
Default value: \fB5\fR.
.RE
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 17:49:50 +00:00
.sp
.ne 2
.na
\fBdbuf_metadata_cache_shift\fR (int)
.ad
.RS 12n
Set the size of the dbuf metadata cache, \fBdbuf_metadata_cache_max_bytes\fR,
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
to a log2 fraction of the target ARC size.
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 17:49:50 +00:00
.sp
Default value: \fB6\fR.
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBdmu_object_alloc_chunk_shift\fR (int)
.ad
.RS 12n
dnode slots allocated in a single operation as a power of 2. The default value
minimizes lock contention for the bulk operation performed.
.sp
Default value: \fB7\fR (128).
.RE
fat zap should prefetch when iterating When iterating over a ZAP object, we're almost always certain to iterate over the entire object. If there are multiple leaf blocks, we can realize a performance win by issuing reads for all the leaf blocks in parallel when the iteration begins. For example, if we have 10,000 snapshots, "zfs destroy -nv pool/fs@1%9999" can take 30 minutes when the cache is cold. This change provides a >3x performance improvement, by issuing the reads for all ~64 blocks of each ZAP object in parallel. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-58347 Closes #8862
2019-06-12 20:13:09 +00:00
.sp
.ne 2
.na
\fBdmu_prefetch_max\fR (int)
.ad
.RS 12n
Limit the amount we can prefetch with one call to this amount (in bytes).
This helps to limit the amount of memory that can be used by prefetching.
.sp
Default value: \fB134,217,728\fR (128MB).
.RE
Add tunable to ignore hole_birth Adds a module option which disables the hole_birth optimization which has been responsible for several recent bugs, including issue #4050. Original-patch: https://gist.github.com/pcd1193182/2c0cd47211f3aee623958b4698836c48 Signed-off-by: Rich Ercolani <rincebrain@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4833
2016-07-08 20:51:50 +00:00
.sp
.ne 2
.na
\fBignore_hole_birth\fR (int)
.ad
.RS 12n
Document send_holes_without_birth_time Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Laager <rlaager@wiktel.com> Closes #8641
2019-04-19 01:15:58 +00:00
This is an alias for \fBsend_holes_without_birth_time\fR.
Add tunable to ignore hole_birth Adds a module option which disables the hole_birth optimization which has been responsible for several recent bugs, including issue #4050. Original-patch: https://gist.github.com/pcd1193182/2c0cd47211f3aee623958b4698836c48 Signed-off-by: Rich Ercolani <rincebrain@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4833
2016-07-08 20:51:50 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBl2arc_feed_again\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Turbo L2ARC warm-up. When the L2ARC is cold the fill interval will be set as
fast as possible.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
.sp
.ne 2
.na
\fBl2arc_feed_min_ms\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Min feed interval in milliseconds. Requires \fBl2arc_feed_again=1\fR and only
applicable in related situations.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB200\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_feed_secs\fR (ulong)
.ad
.RS 12n
Seconds between L2ARC writing
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_headroom\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
How far through the ARC lists to search for L2ARC cacheable content, expressed
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
as a multiplier of \fBl2arc_write_max\fR.
ARC persistence across reboots can be achieved with persistent L2ARC by setting
this parameter to \fB0\fR allowing the full length of ARC lists to be searched
for cacheable content.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_headroom_boost\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Scales \fBl2arc_headroom\fR by this percentage when L2ARC contents are being
Trim L2ARC The l2arc_evict() function is responsible for evicting buffers which reference the next bytes of the L2ARC device to be overwritten. Teach this function to additionally TRIM that vdev space before it is overwritten if the device has been filled with data. This is done by vdev_trim_simple() which trims by issuing a new type of TRIM, TRIM_TYPE_SIMPLE. We also implement a "Trim Ahead" feature. It is a zfs module parameter, expressed in % of the current write size. This trims ahead of the current write size. A minimum of 64MB will be trimmed. The default is 0 which disables TRIM on L2ARC as it can put significant stress to underlying storage devices. To enable TRIM on L2ARC we set l2arc_trim_ahead > 0. We also implement TRIM of the whole cache device upon addition to a pool, pool creation or when the header of the device is invalid upon importing a pool or onlining a cache device. This is dependent on l2arc_trim_ahead > 0. TRIM of the whole device is done with TRIM_TYPE_MANUAL so that its status can be monitored by zpool status -t. We save the TRIM state for the whole device and the time of completion on-disk in the header, and restore these upon L2ARC rebuild so that zpool status -t can correctly report them. Whole device TRIM is done asynchronously so that the user can export of the pool or remove the cache device while it is trimming (ie if it is too slow). We do not TRIM the whole device if persistent L2ARC has been disabled by l2arc_rebuild_enabled = 0 because we may not want to lose all cached buffers (eg we may want to import the pool with l2arc_rebuild_enabled = 0 only once because of memory pressure). If persistent L2ARC has been disabled by setting the module parameter l2arc_rebuild_blocks_min_l2size to a value greater than the size of the cache device then the whole device is trimmed upon creation or import of a pool if l2arc_trim_ahead > 0. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Adam D. Moss <c@yotes.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #9713 Closes #9789 Closes #10224
2020-06-09 17:15:08 +00:00
successfully compressed before writing. A value of \fB100\fR disables this
feature.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB200\fR%.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Introduce ZFS module parameter l2arc_mfuonly In certain workloads it may be beneficial to reduce wear of L2ARC devices by not caching MRU metadata and data into L2ARC. This commit introduces a new tunable l2arc_mfuonly for this purpose. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10710
2020-09-08 18:44:37 +00:00
.sp
.ne 2
.na
\fBl2arc_mfuonly\fR (int)
.ad
.RS 12n
Controls whether only MFU metadata and data are cached from ARC into L2ARC.
This may be desired to avoid wasting space on L2ARC when reading/writing large
amounts of data that are not expected to be accessed more than once. The
default is \fB0\fR, meaning both MRU and MFU data and metadata are cached.
When turning off (\fB0\fR) this feature some MRU buffers will still be present
Add L2ARC arcstats for MFU/MRU buffers and buffer content type Currently the ARC state (MFU/MRU) of cached L2ARC buffer and their content type is unknown. Knowing this information may prove beneficial in adjusting the L2ARC caching policy. This commit adds L2ARC arcstats that display the aligned size (in bytes) of L2ARC buffers according to their content type (data/metadata) and according to their ARC state (MRU/MFU or prefetch). It also expands the existing evict_l2_eligible arcstat to differentiate between MFU and MRU buffers. L2ARC caches buffers from the MRU and MFU lists of ARC. Upon caching a buffer, its ARC state (MRU/MFU) is stored in the L2 header (b_arcs_state). The l2_m{f,r}u_asize arcstats reflect the aligned size (in bytes) of L2ARC buffers according to their ARC state (based on b_arcs_state). We also account for the case where an L2ARC and ARC cached MRU or MRU_ghost buffer transitions to MFU. The l2_prefetch_asize reflects the alinged size (in bytes) of L2ARC buffers that were cached while they had the prefetch flag set in ARC. This is dynamically updated as the prefetch flag of L2ARC buffers changes. When buffers are evicted from ARC, if they are determined to be L2ARC eligible then their logical size is recorded in evict_l2_eligible_m{r,f}u arcstats according to their ARC state upon eviction. Persistent L2ARC: When committing an L2ARC buffer to a log block (L2ARC metadata) its b_arcs_state and prefetch flag is also stored. If the buffer changes its arcstate or prefetch flag this is reflected in the above arcstats. However, the L2ARC metadata cannot currently be updated to reflect this change. Example: L2ARC caches an MRU buffer. L2ARC metadata and arcstats count this as an MRU buffer. The buffer transitions to MFU. The arcstats are updated to reflect this. Upon pool re-import or on/offlining the L2ARC device the arcstats are cleared and the buffer will now be counted as an MRU buffer, as the L2ARC metadata were not updated. Bug fix: - If l2arc_noprefetch is set, arc_read_done clears the L2CACHE flag of an ARC buffer. However, prefetches may be issued in a way that arc_read_done() is bypassed. Instead, move the related code in l2arc_write_eligible() to account for those cases too. Also add a test and update manpages for l2arc_mfuonly module parameter, and update the manpages and code comments for l2arc_noprefetch. Move persist_l2arc tests to l2arc. Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10743
2020-09-14 17:10:44 +00:00
in ARC and eventually cached on L2ARC. If \fBl2arc_noprefetch\fR is set to 0,
some prefetched buffers will be cached to L2ARC, and those might later
transition to MRU, in which case the \fBl2arc_mru_asize\fR arcstat will not
be 0. Regardless of \fBl2arc_noprefetch\fR, some MFU buffers might be evicted
from ARC, accessed later on as prefetches and transition to MRU as prefetches.
If accessed again they are counted as MRU and the \fBl2arc_mru_asize\fR arcstat
will not be 0. The ARC status of L2ARC buffers when they were first cached in
L2ARC can be seen in the \fBl2arc_mru_asize\fR, \fBl2arc_mfu_asize\fR and
\fBl2arc_prefetch_asize\fR arcstats when importing the pool or onlining a cache
Update documentation of l2arc_mfuonly with regard to evicted_l2_eligibile_mru. Even if l2arc_mfuonly is enabled, this is not reflected in evicted_l2_eligible_mru as this information is useful for deciding whether to toggle l2arc_mfuonly depending on the current workload. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10945
2020-09-21 16:26:24 +00:00
device if persistent L2ARC is enabled. The \fBevicted_l2_eligible_mru\fR
arcstat does not take into account if this option is enabled as the information
provided by the evicted_l2_eligible_* arcstats can be used to decide if
toggling this option is appropriate for the current workload.
Introduce ZFS module parameter l2arc_mfuonly In certain workloads it may be beneficial to reduce wear of L2ARC devices by not caching MRU metadata and data into L2ARC. This commit introduces a new tunable l2arc_mfuonly for this purpose. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10710
2020-09-08 18:44:37 +00:00
.sp
Use \fB0\fR for no (default) and \fB1\fR for yes.
.RE
Introduce limit on size of L2ARC headers Since L2ARC buffers are not evicted on memory pressure, too large amount of headers on system with irrationally large L2ARC can render it slow or even unusable. This change limits L2ARC writes and rebuild if unevictable L2ARC-only headers reach dangerous level. While there, call arc_adapt() on L2ARC rebuild, so that it could properly grow arc_c, reflecting potentially significant ARC size increase and avoiding slow growth with hopeless eviction attempts later when "overflow" is detected. Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reported-by: Richard Elling <Richard.Elling@RichardElling.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Closes #10765
2020-08-25 21:33:36 +00:00
.sp
.ne 2
.na
\fBl2arc_meta_percent\fR (int)
.ad
.RS 12n
Percent of ARC size allowed for L2ARC-only headers.
Since L2ARC buffers are not evicted on memory pressure, too large amount of
headers on system with irrationaly large L2ARC can render it slow or unusable.
This parameter limits L2ARC writes and rebuild to achieve it.
.sp
Default value: \fB33\fR%.
.RE
Trim L2ARC The l2arc_evict() function is responsible for evicting buffers which reference the next bytes of the L2ARC device to be overwritten. Teach this function to additionally TRIM that vdev space before it is overwritten if the device has been filled with data. This is done by vdev_trim_simple() which trims by issuing a new type of TRIM, TRIM_TYPE_SIMPLE. We also implement a "Trim Ahead" feature. It is a zfs module parameter, expressed in % of the current write size. This trims ahead of the current write size. A minimum of 64MB will be trimmed. The default is 0 which disables TRIM on L2ARC as it can put significant stress to underlying storage devices. To enable TRIM on L2ARC we set l2arc_trim_ahead > 0. We also implement TRIM of the whole cache device upon addition to a pool, pool creation or when the header of the device is invalid upon importing a pool or onlining a cache device. This is dependent on l2arc_trim_ahead > 0. TRIM of the whole device is done with TRIM_TYPE_MANUAL so that its status can be monitored by zpool status -t. We save the TRIM state for the whole device and the time of completion on-disk in the header, and restore these upon L2ARC rebuild so that zpool status -t can correctly report them. Whole device TRIM is done asynchronously so that the user can export of the pool or remove the cache device while it is trimming (ie if it is too slow). We do not TRIM the whole device if persistent L2ARC has been disabled by l2arc_rebuild_enabled = 0 because we may not want to lose all cached buffers (eg we may want to import the pool with l2arc_rebuild_enabled = 0 only once because of memory pressure). If persistent L2ARC has been disabled by setting the module parameter l2arc_rebuild_blocks_min_l2size to a value greater than the size of the cache device then the whole device is trimmed upon creation or import of a pool if l2arc_trim_ahead > 0. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Adam D. Moss <c@yotes.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #9713 Closes #9789 Closes #10224
2020-06-09 17:15:08 +00:00
.sp
.ne 2
.na
\fBl2arc_trim_ahead\fR (ulong)
.ad
.RS 12n
Trims ahead of the current write size (\fBl2arc_write_max\fR) on L2ARC devices
by this percentage of write size if we have filled the device. If set to
\fB100\fR we TRIM twice the space required to accommodate upcoming writes. A
minimum of 64MB will be trimmed. It also enables TRIM of the whole L2ARC device
upon creation or addition to an existing pool or if the header of the device is
invalid upon importing a pool or onlining a cache device. A value of \fB0\fR
disables TRIM on L2ARC altogether and is the default as it can put significant
stress on the underlying storage devices. This will vary depending of how well
the specific device handles these commands.
.sp
Default value: \fB0\fR%.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBl2arc_noprefetch\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Do not write buffers to L2ARC if they were prefetched but not used by
Add L2ARC arcstats for MFU/MRU buffers and buffer content type Currently the ARC state (MFU/MRU) of cached L2ARC buffer and their content type is unknown. Knowing this information may prove beneficial in adjusting the L2ARC caching policy. This commit adds L2ARC arcstats that display the aligned size (in bytes) of L2ARC buffers according to their content type (data/metadata) and according to their ARC state (MRU/MFU or prefetch). It also expands the existing evict_l2_eligible arcstat to differentiate between MFU and MRU buffers. L2ARC caches buffers from the MRU and MFU lists of ARC. Upon caching a buffer, its ARC state (MRU/MFU) is stored in the L2 header (b_arcs_state). The l2_m{f,r}u_asize arcstats reflect the aligned size (in bytes) of L2ARC buffers according to their ARC state (based on b_arcs_state). We also account for the case where an L2ARC and ARC cached MRU or MRU_ghost buffer transitions to MFU. The l2_prefetch_asize reflects the alinged size (in bytes) of L2ARC buffers that were cached while they had the prefetch flag set in ARC. This is dynamically updated as the prefetch flag of L2ARC buffers changes. When buffers are evicted from ARC, if they are determined to be L2ARC eligible then their logical size is recorded in evict_l2_eligible_m{r,f}u arcstats according to their ARC state upon eviction. Persistent L2ARC: When committing an L2ARC buffer to a log block (L2ARC metadata) its b_arcs_state and prefetch flag is also stored. If the buffer changes its arcstate or prefetch flag this is reflected in the above arcstats. However, the L2ARC metadata cannot currently be updated to reflect this change. Example: L2ARC caches an MRU buffer. L2ARC metadata and arcstats count this as an MRU buffer. The buffer transitions to MFU. The arcstats are updated to reflect this. Upon pool re-import or on/offlining the L2ARC device the arcstats are cleared and the buffer will now be counted as an MRU buffer, as the L2ARC metadata were not updated. Bug fix: - If l2arc_noprefetch is set, arc_read_done clears the L2CACHE flag of an ARC buffer. However, prefetches may be issued in a way that arc_read_done() is bypassed. Instead, move the related code in l2arc_write_eligible() to account for those cases too. Also add a test and update manpages for l2arc_mfuonly module parameter, and update the manpages and code comments for l2arc_noprefetch. Move persist_l2arc tests to l2arc. Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10743
2020-09-14 17:10:44 +00:00
applications. In case there are prefetched buffers in L2ARC and this option
is later set to \fB1\fR, we do not read the prefetched buffers from L2ARC.
Setting this option to \fB0\fR is useful for caching sequential reads from the
disks to L2ARC and serve those reads from L2ARC later on. This may be beneficial
in case the L2ARC device is significantly faster in sequential reads than the
disks of the pool.
.sp
Use \fB1\fR to disable (default) and \fB0\fR to enable caching/reading
prefetches to/from L2ARC..
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBl2arc_norw\fR (int)
.ad
.RS 12n
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
No reads during writes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBl2arc_write_boost\fR (ulong)
.ad
.RS 12n
Fix typo in zfs-module-parameters man page Fix typo in zfs-module-parameters man page Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Mike McQuaid <mike@mikemcquaid.com> Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Neal Gompa <ngompa13@gmail.com> Reviewed-by: Jason Zaman <jason@perfinion.com> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Hajo Möller <dasjoe@gmail.com> Reviewed-by: Igor Kozhukhov <ikozhukhov@gmail.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: DHE <git@dehacked.net> Reviewed-by: Matthew Thode <prometheanfire@gentoo.org> Reviewed-by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: kernelOfTruth <kerneloftruth@gmail.com> Reviewed-by: Kash Pande <kash@tripleback.net> Reviewed-by: ilovezfs <ilovezfs@icloud.com> Reviewed-by: @jwittlincohen Reviewed-by: Jack Draak <jackdraak@gmail.com> Reviewed-by: @ptx0 Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: @Kokokokoka Reviewed-by: @JCount <JCount@hush.ai> Signed-off-by: bunder2015 <omfgbunder@gmail.com> Closes #6054
2017-04-24 17:56:44 +00:00
Cold L2ARC devices will have \fBl2arc_write_max\fR increased by this amount
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
while they remain cold.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB8,388,608\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_write_max\fR (ulong)
.ad
.RS 12n
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
Max write bytes per interval.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB8,388,608\fR.
.RE
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
.sp
.ne 2
.na
\fBl2arc_rebuild_enabled\fR (int)
.ad
.RS 12n
Rebuild the L2ARC when importing a pool (persistent L2ARC). This can be
disabled if there are problems importing a pool or attaching an L2ARC device
(e.g. the L2ARC device is slow in reading stored log metadata, or the metadata
has become somehow fragmented/unusable).
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
.sp
.ne 2
.na
\fBl2arc_rebuild_blocks_min_l2size\fR (ulong)
.ad
.RS 12n
Min size (in bytes) of an L2ARC device required in order to write log blocks
in it. The log blocks are used upon importing the pool to rebuild
the L2ARC (persistent L2ARC). Rationale: for L2ARC devices less than 1GB, the
amount of data l2arc_evict() evicts is significant compared to the amount of
restored L2ARC data. In this case do not write log blocks in L2ARC in order not
to waste space.
.sp
Default value: \fB1,073,741,824\fR (1GB).
.RE
Make metaslab_aliquot a module parameter. This seems generally useful. metaslab_aliquot is the ZFS allocation granularity, which is roughly equivalent to what is called the stripe size in traditional RAID arrays. It seems relevant to performance tuning. Signed-off-by: Etienne Dechamps <etienne@edechamps.fr> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-05-10 15:40:20 +00:00
.sp
.ne 2
.na
\fBmetaslab_aliquot\fR (ulong)
.ad
.RS 12n
Metaslab granularity, in bytes. This is roughly similar to what would be
referred to as the "stripe size" in traditional RAID arrays. In normal
operation, ZFS will try to write this amount of data to a top-level vdev
before moving on to the next one.
.sp
Default value: \fB524,288\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
.sp
.ne 2
.na
\fBmetaslab_bias_enabled\fR (int)
.ad
.RS 12n
Enable metaslab group biasing based on its vdev's over- or under-utilization
relative to the pool.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
OpenZFS 9280 - Assertion failure while running removal_with_ganging test with 4K devices Authored by: Matt Ahrens <Matt.Ahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9280 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/243952c Closes #7445
2017-07-24 18:07:39 +00:00
.sp
.ne 2
.na
\fBmetaslab_force_ganging\fR (ulong)
.ad
.RS 12n
Make some blocks above a certain size be gang blocks. This option is used
by the test suite to facilitate testing.
.sp
Default value: \fB16,777,217\fR.
.RE
Assertion failure when logging large output of channel program The output of ZFS channel programs is logged on-disk in the zpool history, and printed by `zpool history -i`. Channel programs can use 10MB of memory by default, and up to 100MB by using the `zfs program -m` flag. Therefore their output can be up to some fraction of 100MB. In addition to being somewhat wasteful of the limited space reserved for the pool history (which for large pools is 1GB), in extreme cases this can result in a failure of `ASSERT(length <= DMU_MAX_ACCESS);` in `dmu_buf_hold_array_by_dnode()`. This commit limits the output size that will be logged to 1MB. Larger outputs will not be logged, instead a entry will be logged indicating the size of the omitted output. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11194
2020-11-14 18:17:16 +00:00
.sp
.ne 2
.na
\fBzfs_history_output_max\fR (int)
.ad
.RS 12n
When attempting to log the output nvlist of an ioctl in the on-disk history, the
output will not be stored if it is larger than size (in bytes). This must be
less then DMU_MAX_ACCESS (64MB). This applies primarily to
zfs_ioc_channel_program().
.sp
Default value: \fB1MB\fR.
.RE
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
.sp
.ne 2
.na
\fBzfs_keep_log_spacemaps_at_export\fR (int)
.ad
.RS 12n
Prevent log spacemaps from being destroyed during pool exports and destroys.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
OpenZFS 7303 - dynamic metaslab selection This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404
2017-01-12 19:52:56 +00:00
.sp
.ne 2
.na
\fBzfs_metaslab_segment_weight_enabled\fR (int)
.ad
.RS 12n
Enable/disable segment-based metaslab selection.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
.sp
.ne 2
.na
\fBzfs_metaslab_switch_threshold\fR (int)
.ad
.RS 12n
When using segment-based metaslab selection, continue allocating
Typo in zfs-module-parameters(5) Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #6061
2017-04-24 17:34:37 +00:00
from the active metaslab until \fBzfs_metaslab_switch_threshold\fR
OpenZFS 7303 - dynamic metaslab selection This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404
2017-01-12 19:52:56 +00:00
worth of buckets have been exhausted.
.sp
Default value: \fB2\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
Illumos #4101 finer-grained control of metaslab_debug Today the metaslab_debug logic performs two tasks: - load all metaslabs on import/open - don't unload metaslabs at the end of spa_sync This change provides knobs for each of these independently. References: https://illumos.org/issues/4101 https://github.com/illumos/illumos-gate/commit/0713e23 Notes: 1) This is a small piece of the metaslab improvement patch from Illumos. It was worth bringing over before the rest, since it's low risk and it can be useful on fragmented pools (e.g. Lustre MDTs). metaslab_debug_unload would give the performance benefit of the old metaslab_debug option without causing unwanted delay during pool import. Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2227
2014-04-01 00:22:55 +00:00
\fBmetaslab_debug_load\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Illumos #4101 finer-grained control of metaslab_debug Today the metaslab_debug logic performs two tasks: - load all metaslabs on import/open - don't unload metaslabs at the end of spa_sync This change provides knobs for each of these independently. References: https://illumos.org/issues/4101 https://github.com/illumos/illumos-gate/commit/0713e23 Notes: 1) This is a small piece of the metaslab improvement patch from Illumos. It was worth bringing over before the rest, since it's low risk and it can be useful on fragmented pools (e.g. Lustre MDTs). metaslab_debug_unload would give the performance benefit of the old metaslab_debug option without causing unwanted delay during pool import. Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2227
2014-04-01 00:22:55 +00:00
Load all metaslabs during pool import.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBmetaslab_debug_unload\fR (int)
.ad
.RS 12n
Prevent metaslabs from being unloaded.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
.sp
.ne 2
.na
\fBmetaslab_fragmentation_factor_enabled\fR (int)
.ad
.RS 12n
Enable use of the fragmentation metric in computing metaslab weights.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
looping in metaslab_block_picker impacts performance on fragmented pools On fragmented pools with high-performance storage, the looping in metaslab_block_picker() can become the performance-limiting bottleneck. When looking for a larger block (e.g. a 128K block for the ZIL), we may search through many free segments (up to hundreds of thousands) to find one that is large enough to satisfy the allocation. This can take a long time (up to dozens of ms), and is done while holding the ms_lock, which other threads may spin waiting for. When this performance problem is encountered, profiling will show high CPU time in metaslab_block_picker, as well as in mutex_enter from various callers. The problem is very evident on a test system with a sync write workload with 8K writes to a recordsize=8k filesystem, with 4TB of SSD storage, 84% full and 88% fragmented. It has also been observed on production systems with 90TB of storage, 76% full and 87% fragmented. The fix is to change metaslab_df_alloc() to search only up to 16MB from the previous allocation (of this alignment). After that, we will pick a segment that is of the exact size requested (or larger). This reduces the number of iterations to a few hundred on fragmented pools (a ~100x improvement). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-62324 Closes #8877
2019-06-13 20:06:15 +00:00
.sp
.ne 2
.na
\fBmetaslab_df_max_search\fR (int)
.ad
.RS 12n
Maximum distance to search forward from the last offset. Without this limit,
fragmented pools can see >100,000 iterations and metaslab_block_picker()
becomes the performance limiting factor on high-performance storage.
With the default setting of 16MB, we typically see less than 500 iterations,
even with very fragmented, ashift=9 pools. The maximum number of iterations
possible is: \fBmetaslab_df_max_search / (2 * (1<<ashift))\fR.
With the default setting of 16MB this is 16*1024 (with ashift=9) or 2048
(with ashift=12).
.sp
Default value: \fB16,777,216\fR (16MB)
.RE
.sp
.ne 2
.na
\fBmetaslab_df_use_largest_segment\fR (int)
.ad
.RS 12n
If we are not searching forward (due to metaslab_df_max_search,
metaslab_df_free_pct, or metaslab_df_alloc_threshold), this tunable controls
man: Canonicalize .TH usage * Use all caps for document title. * Remove section name as it can be inferred from the section number. * Name "OpenZFS" as the document source. * Bump modification date. While here, fixed trailing whitespace reported by igor. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10792
2020-08-25 04:25:28 +00:00
what segment is used. If it is set, we will use the largest free segment.
looping in metaslab_block_picker impacts performance on fragmented pools On fragmented pools with high-performance storage, the looping in metaslab_block_picker() can become the performance-limiting bottleneck. When looking for a larger block (e.g. a 128K block for the ZIL), we may search through many free segments (up to hundreds of thousands) to find one that is large enough to satisfy the allocation. This can take a long time (up to dozens of ms), and is done while holding the ms_lock, which other threads may spin waiting for. When this performance problem is encountered, profiling will show high CPU time in metaslab_block_picker, as well as in mutex_enter from various callers. The problem is very evident on a test system with a sync write workload with 8K writes to a recordsize=8k filesystem, with 4TB of SSD storage, 84% full and 88% fragmented. It has also been observed on production systems with 90TB of storage, 76% full and 87% fragmented. The fix is to change metaslab_df_alloc() to search only up to 16MB from the previous allocation (of this alignment). After that, we will pick a segment that is of the exact size requested (or larger). This reduces the number of iterations to a few hundred on fragmented pools (a ~100x improvement). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-62324 Closes #8877
2019-06-13 20:06:15 +00:00
If it is not set, we will use a segment of exactly the requested size (or
larger).
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Metaslab max_size should be persisted while unloaded When we unload metaslabs today in ZFS, the cached max_size value is discarded. We instead use the histogram to determine whether or not we think we can satisfy an allocation from the metaslab. This can result in situations where, if we're doing I/Os of a size not aligned to a histogram bucket, a metaslab is loaded even though it cannot satisfy the allocation we think it can. For example, a metaslab with 16 entries in the 16k-32k bucket may have entirely 16kB entries. If we try to allocate a 24kB buffer, we will load that metaslab because we think it should be able to handle the allocation. Doing so is expensive in CPU time, disk reads, and average IO latency. This is exacerbated if the write being attempted is a sync write. This change makes ZFS cache the max_size after the metaslab is unloaded. If we ever get a free (or a coalesced group of frees) larger than the max_size, we will update it. Otherwise, we leave it as is. When attempting to allocate, we use the max_size as a lower bound, and respect it unless we are in try_hard. However, we do age the max_size out at some point, since we expect the actual max_size to increase as we do more frees. A more sophisticated algorithm here might be helpful, but this works reasonably well. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #9055
2019-08-05 21:34:27 +00:00
.sp
.ne 2
.na
\fBzfs_metaslab_max_size_cache_sec\fR (ulong)
.ad
.RS 12n
When we unload a metaslab, we cache the size of the largest free chunk. We use
that cached size to determine whether or not to load a metaslab for a given
allocation. As more frees accumulate in that metaslab while it's unloaded, the
cached max size becomes less and less accurate. After a number of seconds
controlled by this tunable, we stop considering the cached max size and start
considering only the histogram instead.
.sp
Default value: \fB3600 seconds\fR (one hour)
.RE
Cap metaslab memory usage On systems with large amounts of storage and high fragmentation, a huge amount of space can be used by storing metaslab range trees. Since metaslabs are only unloaded during a txg sync, and only if they have been inactive for 8 txgs, it is possible to get into a state where all of the system's memory is consumed by range trees and metaslabs, and txgs cannot sync. While ZFS knows how to evict ARC data when needed, it has no such mechanism for range tree data. This can result in boot hangs for some system configurations. First, we add the ability to unload metaslabs outside of syncing context. Second, we store a multilist of all loaded metaslabs, sorted by their selection txg, so we can quickly identify the oldest metaslabs. We use a multilist to reduce lock contention during heavy write workloads. Finally, we add logic that will unload a metaslab when we're loading a new metaslab, if we're using more than a certain fraction of the available memory on range trees. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #9128
2019-08-16 15:08:21 +00:00
.sp
.ne 2
.na
\fBzfs_metaslab_mem_limit\fR (int)
.ad
.RS 12n
When we are loading a new metaslab, we check the amount of memory being used
to store metaslab range trees. If it is over a threshold, we attempt to unload
the least recently used metaslab to prevent the system from clogging all of
its memory with range trees. This tunable sets the percentage of total system
memory that is the threshold.
.sp
Keep more metaslabs loaded With the other metaslab changes loaded onto a system, we can significantly reduce the memory usage of each loaded metaslab and unload them on demand if there is memory pressure. However, none of those changes actually result in us keeping more metaslabs loaded. If we don't keep more metaslabs loaded, we will still have to wait for demand-loading to finish when no loaded metaslab can satisfy our allocation, which can cause ZIL performance issues. In addition, performance is traditionally measured by IOs per unit time, while unloading is currently done on a txg-count basis. Txgs can take a widely varying range of times, from tenths of a second to several seconds. This can result in confusing, hard to predict behavior. This change simply adds a time-based component to metaslab unloading. A metaslab will remain loaded for one minute and 8 txgs (by default) after it was last used, unless it is evicted due to memory pressure. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> External-issue: DLPX-65016 External-issue: DLPX-65047 Closes #9197
2019-08-29 17:20:36 +00:00
Default value: \fB25 percent\fR
Cap metaslab memory usage On systems with large amounts of storage and high fragmentation, a huge amount of space can be used by storing metaslab range trees. Since metaslabs are only unloaded during a txg sync, and only if they have been inactive for 8 txgs, it is possible to get into a state where all of the system's memory is consumed by range trees and metaslabs, and txgs cannot sync. While ZFS knows how to evict ARC data when needed, it has no such mechanism for range tree data. This can result in boot hangs for some system configurations. First, we add the ability to unload metaslabs outside of syncing context. Second, we store a multilist of all loaded metaslabs, sorted by their selection txg, so we can quickly identify the oldest metaslabs. We use a multilist to reduce lock contention during heavy write workloads. Finally, we add logic that will unload a metaslab when we're loading a new metaslab, if we're using more than a certain fraction of the available memory on range trees. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #9128
2019-08-16 15:08:21 +00:00
.RE
Only examine best metaslabs on each vdev On a system with very high fragmentation, we may need to do lots of gang allocations (e.g. most indirect block allocations (~50KB) may need to gang). Before failing a "normal" allocation and resorting to ganging, we try every metaslab. This has the impact of loading every metaslab (not a huge deal since we now typically keep all metaslabs loaded), and also iterating over every metaslab for every failing allocation. If there are many metaslabs (more than the typical ~200, e.g. due to vdev expansion or very large vdevs), the CPU cost of this iteration can be very impactful. This iteration is done with the mg_lock held, creating long hold times and high lock contention for concurrent allocations, ultimately causing long txg sync times and poor application performance. To address this, this commit changes the behavior of "normal" (not try_hard, not ZIL) allocations. These will now only examine the 100 best metaslabs (as determined by their ms_weight). If none of these have a large enough free segment, then the allocation will fail and we'll fall back on ganging. To accomplish this, we will now (normally) gang before doing a `try_hard` allocation. Non-try_hard allocations will only examine the 100 best metaslabs of each vdev. In summary, we will first try normal allocation. If that fails then we will do a gang allocation. If that fails then we will do a "try hard" gang allocation. If that fails then we will have a multi-layer gang block. Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11327
2020-12-16 22:40:05 +00:00
.sp
.ne 2
.na
\fBzfs_metaslab_try_hard_before_gang\fR (int)
.ad
.RS 12n
If not set (the default), we will first try normal allocation.
If that fails then we will do a gang allocation.
If that fails then we will do a "try hard" gang allocation.
If that fails then we will have a multi-layer gang block.
.sp
If set, we will first try normal allocation.
If that fails then we will do a "try hard" allocation.
If that fails we will do a gang allocation.
If that fails we will do a "try hard" gang allocation.
If that fails then we will have a multi-layer gang block.
.sp
Default value: \fB0 (false)\fR
.RE
.sp
.ne 2
.na
\fBzfs_metaslab_find_max_tries\fR (int)
.ad
.RS 12n
When not trying hard, we only consider this number of the best metaslabs.
This improves performance, especially when there are many metaslabs per vdev
and the allocation can't actually be satisfied (so we would otherwise iterate
all the metaslabs).
.sp
Default value: \fB100\fR
.RE
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 14:13:00 +00:00
.sp
.ne 2
.na
Change target size of metaslabs from 256GB to 16GB = Old behavior For vdev sizes 100GB to 50TB we keep ~200 metaslabs per vdev and the metaslab size grows from 512MB to 256GB. For vdev's bigger than that we start increasing the number of metaslabs until we hit the 128K limit. = New Behavior For vdev sizes 100GB to 3TB we keep ~200 metaslabs per vdev and the metaslab size grows from 512MB to 16GB. For vdev's bigger than that we start increasing the number of metaslabs until we hit the 128K limit. = Reasoning The old behavior makes metaslabs grow in size when the vdev range is between 3TB (ms_size 16GB) and 32PB (ms_size 256GB). Even though keeping the number of metaslabs is good in terms of potential number of I/Os per TXG, these bigger metaslabs take longer to be loaded and after they are loaded they can take up a lot of memory because of their range trees. This change tries to put a boundary in memory and loading time for the specific range of vdev sizes. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Don Brady <don.brady@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8324
2019-01-26 00:38:27 +00:00
\fBzfs_vdev_default_ms_count\fR (int)
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 14:13:00 +00:00
.ad
.RS 12n
OpenZFS 9426 - metaslab size can exceed offset addressable by spacemap Authored by: Don Brady <don.brady@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@joyent.com> OpenZFS-issue: https://www.illumos.org/issues/9426 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f1c88afb1 Closes #7700
2017-08-11 21:28:17 +00:00
When a vdev is added target this number of metaslabs per top-level vdev.
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 14:13:00 +00:00
.sp
Default value: \fB200\fR.
.RE
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_default_ms_shift\fR (int)
.ad
.RS 12n
Default limit for metaslab size.
.sp
Default value: \fB29\fR [meaning (1 << 29) = 512MB].
.RE
Import vdev ashift optimization from FreeBSD Many modern devices use physical allocation units that are much larger than the minimum logical allocation size accessible by external commands. Two prevalent examples of this are 512e disk drives (512b logical sector, 4K physical sector) and flash devices (512b logical sector, 4K or larger allocation block size, and 128k or larger erase block size). Operations that modify less than the physical sector size result in a costly read-modify-write or garbage collection sequence on these devices. Simply exporting the true physical sector of the device to ZFS would yield optimal performance, but has two serious drawbacks: 1. Existing pools created with devices that have different logical and physical block sizes, but were configured to use the logical block size (e.g. because the OS version used for pool construction reported the logical block size instead of the physical block size) will suddenly find that the vdev allocation size has increased. This can be easily tolerated for active members of the array, but ZFS would prevent replacement of a vdev with another identical device because it now appears that the smaller allocation size required by the pool is not supported by the new device. 2. The device's physical block size may be too large to be supported by ZFS. The optimal allocation size for the vdev may be quite large. For example, a RAID controller may export a vdev that requires read-modify-write cycles unless accessed using 64k aligned/sized requests. ZFS currently has an 8k minimum block size limit. Reporting both the logical and physical allocation sizes for vdevs solves these problems. A device may be used so long as the logical block size is compatible with the configuration. By comparing the logical and physical block sizes, new configurations can be optimized and administrators can be notified of any existing pools that are sub-optimal. Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Matthew Macy <mmacy@freebsd.org> Signed-off-by: Matt Macy <mmacy@FreeBSD.org> Closes #10619
2020-08-21 19:53:17 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_max_auto_ashift\fR (ulong)
.ad
.RS 12n
Maximum ashift used when optimizing for logical -> physical sector size on new
top-level vdevs.
.sp
Default value: \fBASHIFT_MAX\fR (16).
.RE
.sp
.ne 2
.na
\fBzfs_vdev_min_auto_ashift\fR (ulong)
.ad
.RS 12n
Minimum ashift used when creating new top-level vdevs.
.sp
Default value: \fBASHIFT_MIN\fR (9).
.RE
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-16 22:11:29 +00:00
.sp
.ne 2
.na
Change target size of metaslabs from 256GB to 16GB = Old behavior For vdev sizes 100GB to 50TB we keep ~200 metaslabs per vdev and the metaslab size grows from 512MB to 256GB. For vdev's bigger than that we start increasing the number of metaslabs until we hit the 128K limit. = New Behavior For vdev sizes 100GB to 3TB we keep ~200 metaslabs per vdev and the metaslab size grows from 512MB to 16GB. For vdev's bigger than that we start increasing the number of metaslabs until we hit the 128K limit. = Reasoning The old behavior makes metaslabs grow in size when the vdev range is between 3TB (ms_size 16GB) and 32PB (ms_size 256GB). Even though keeping the number of metaslabs is good in terms of potential number of I/Os per TXG, these bigger metaslabs take longer to be loaded and after they are loaded they can take up a lot of memory because of their range trees. This change tries to put a boundary in memory and loading time for the specific range of vdev sizes. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Don Brady <don.brady@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8324
2019-01-26 00:38:27 +00:00
\fBzfs_vdev_min_ms_count\fR (int)
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-16 22:11:29 +00:00
.ad
.RS 12n
Minimum number of metaslabs to create in a top-level vdev.
.sp
Default value: \fB16\fR.
.RE
OpenZFS 9426 - metaslab size can exceed offset addressable by spacemap Authored by: Don Brady <don.brady@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@joyent.com> OpenZFS-issue: https://www.illumos.org/issues/9426 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f1c88afb1 Closes #7700
2017-08-11 21:28:17 +00:00
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBvdev_validate_skip\fR (int)
.ad
.RS 12n
Skip label validation steps during pool import. Changing is not recommended
unless you know what you are doing and are recovering a damaged label.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_ms_count_limit\fR (int)
OpenZFS 9426 - metaslab size can exceed offset addressable by spacemap Authored by: Don Brady <don.brady@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@joyent.com> OpenZFS-issue: https://www.illumos.org/issues/9426 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f1c88afb1 Closes #7700
2017-08-11 21:28:17 +00:00
.ad
.RS 12n
Practical upper limit of total metaslabs per top-level vdev.
.sp
Default value: \fB131,072\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
.sp
.ne 2
.na
\fBmetaslab_preload_enabled\fR (int)
.ad
.RS 12n
Enable metaslab group preloading.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
.sp
.ne 2
.na
\fBmetaslab_lba_weighting_enabled\fR (int)
.ad
.RS 12n
Give more weight to metaslabs with lower LBAs, assuming they have
greater bandwidth as is typically the case on a modern constant
angular velocity disk drive.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
Keep more metaslabs loaded With the other metaslab changes loaded onto a system, we can significantly reduce the memory usage of each loaded metaslab and unload them on demand if there is memory pressure. However, none of those changes actually result in us keeping more metaslabs loaded. If we don't keep more metaslabs loaded, we will still have to wait for demand-loading to finish when no loaded metaslab can satisfy our allocation, which can cause ZIL performance issues. In addition, performance is traditionally measured by IOs per unit time, while unloading is currently done on a txg-count basis. Txgs can take a widely varying range of times, from tenths of a second to several seconds. This can result in confusing, hard to predict behavior. This change simply adds a time-based component to metaslab unloading. A metaslab will remain loaded for one minute and 8 txgs (by default) after it was last used, unless it is evicted due to memory pressure. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> External-issue: DLPX-65016 External-issue: DLPX-65047 Closes #9197
2019-08-29 17:20:36 +00:00
.sp
.ne 2
.na
\fBmetaslab_unload_delay\fR (int)
.ad
.RS 12n
After a metaslab is used, we keep it loaded for this many txgs, to attempt to
reduce unnecessary reloading. Note that both this many txgs and
\fBmetaslab_unload_delay_ms\fR milliseconds must pass before unloading will
occur.
.sp
Default value: \fB32\fR.
.RE
.sp
.ne 2
.na
\fBmetaslab_unload_delay_ms\fR (int)
.ad
.RS 12n
After a metaslab is used, we keep it loaded for this many milliseconds, to
attempt to reduce unnecessary reloading. Note that both this many
milliseconds and \fBmetaslab_unload_delay\fR txgs must pass before unloading
will occur.
.sp
Default value: \fB600000\fR (ten minutes).
.RE
Document send_holes_without_birth_time Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Laager <rlaager@wiktel.com> Closes #8641
2019-04-19 01:15:58 +00:00
.sp
.ne 2
.na
Reference_tracking_enable should be a module param To make use of zfs_refcount_held tunable it should be a module parameter in open-zfs. Also, since the macros will auto-generate OS specific tunables, removed the existing zfs_refcount_held reference in module/os/freebsd/zfs/sysctl_os.c. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Allan Jude <allan@klarasystems.com> Signed-off-by: Don Brady <don.brady@delphix.com> Closes #11753
2021-03-16 21:56:17 +00:00
\fBreference_history\fR (int)
.ad
.RS 12n
Maximum reference holders being tracked when reference_tracking_enable is
active.
.sp
Default value: \fB3\fR.
.RE
.sp
.ne 2
.na
\fBreference_tracking_enable\fR (int)
.ad
.RS 12n
Track reference holders to refcount_t objects (debug builds only).
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
Document send_holes_without_birth_time Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Laager <rlaager@wiktel.com> Closes #8641
2019-04-19 01:15:58 +00:00
\fBsend_holes_without_birth_time\fR (int)
.ad
.RS 12n
When set, the hole_birth optimization will not be used, and all holes will
Change wording in zfs-module-parameters.5 Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Laager <rlaager@wiktel.com> Closes #8641
2019-04-21 20:12:30 +00:00
always be sent on zfs send. This is useful if you suspect your datasets are
affected by a bug in hole_birth.
Document send_holes_without_birth_time Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Laager <rlaager@wiktel.com> Closes #8641
2019-04-19 01:15:58 +00:00
.sp
Use \fB1\fR for on (default) and \fB0\fR for off.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBspa_config_path\fR (charp)
.ad
.RS 12n
SPA config file
.sp
Default value: \fB/etc/zfs/zpool.cache\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBspa_asize_inflation\fR (int)
.ad
.RS 12n
Multiplication factor used to estimate actual disk consumption from the
size of data being written. The default value is a worst case estimate,
but lower values may be valid for a given pool depending on its
configuration. Pool administrators who understand the factors involved
may wish to specify a more realistic inflation factor, particularly if
they operate close to quota or capacity limits.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB24\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
OpenZFS 9075 - Improve ZFS pool import/load process and corrupted pool recovery Some work has been done lately to improve the debugability of the ZFS pool load (and import) process. This includes: 7638 Refactor spa_load_impl into several functions 8961 SPA load/import should tell us why it failed 7277 zdb should be able to print zfs_dbgmsg's To iterate on top of that, there's a few changes that were made to make the import process more resilient and crash free. One of the first tasks during the pool load process is to parse a config provided from userland that describes what devices the pool is composed of. A vdev tree is generated from that config, and then all the vdevs are opened. The Meta Object Set (MOS) of the pool is accessed, and several metadata objects that are necessary to load the pool are read. The exact configuration of the pool is also stored inside the MOS. Since the configuration provided from userland is external and might not accurately describe the vdev tree of the pool at the txg that is being loaded, it cannot be relied upon to safely operate the pool. For that reason, the configuration in the MOS is read early on. In the past, the two configurations were compared together and if there was a mismatch then the load process was aborted and an error was returned. The latter was a good way to ensure a pool does not get corrupted, however it made the pool load process needlessly fragile in cases where the vdev configuration changed or the userland configuration was outdated. Since the MOS is stored in 3 copies, the configuration provided by userland doesn't have to be perfect in order to read its contents. Hence, a new approach has been adopted: The pool is first opened with the untrusted userland configuration just so that the real configuration can be read from the MOS. The trusted MOS configuration is then used to generate a new vdev tree and the pool is re-opened. When the pool is opened with an untrusted configuration, writes are disabled to avoid accidentally damaging it. During reads, some sanity checks are performed on block pointers to see if each DVA points to a known vdev; when the configuration is untrusted, instead of panicking the system if those checks fail we simply avoid issuing reads to the invalid DVAs. This new two-step pool load process now allows rewinding pools accross vdev tree changes such as device replacement, addition, etc. Loading a pool from an external config file in a clustering environment also becomes much safer now since the pool will import even if the config is outdated and didn't, for instance, register a recent device addition. With this code in place, it became relatively easy to implement a long-sought-after feature: the ability to import a pool with missing top level (i.e. non-redundant) devices. Note that since this almost guarantees some loss of data, this feature is for now restricted to a read-only import. Porting notes (ZTS): * Fix 'make dist' target in zpool_import * The maximum path length allowed by tar is 99 characters. Several of the new test cases exceeded this limit resulting in them not being included in the tarball. Shorten the names slightly. * Set/get tunables using accessor functions. * Get last synced txg via the "zfs_txg_history" mechanism. * Clear zinject handlers in cleanup for import_cache_device_replaced and import_rewind_device_replaced in order that the zpool can be exported if there is an error. * Increase FILESIZE to 8G in zfs-test.sh to allow for a larger ext4 file system to be created on ZFS_DISK2. Also, there's no need to partition ZFS_DISK2 at all. The partitioning had already been disabled for multipath devices. Among other things, the partitioning steals some space from the ext4 file system, makes it difficult to accurately calculate the paramters to parted and can make some of the tests fail. * Increase FS_SIZE and FILE_SIZE in the zpool_import test configuration now that FILESIZE is larger. * Write more data in order that device evacuation take lonnger in a couple tests. * Use mkdir -p to avoid errors when the directory already exists. * Remove use of sudo in import_rewind_config_changed. Authored by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9075 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/619c0123 Closes #7459
2016-07-22 14:39:36 +00:00
.sp
.ne 2
.na
\fBspa_load_print_vdev_tree\fR (int)
.ad
.RS 12n
Whether to print the vdev tree in the debugging message buffer during pool import.
Use 0 to disable and 1 to enable.
.sp
Default value: \fB0\fR.
.RE
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.sp
.ne 2
.na
\fBspa_load_verify_data\fR (int)
.ad
.RS 12n
Whether to traverse data blocks during an "extreme rewind" (\fB-X\fR)
import. Use 0 to disable and 1 to enable.
An extreme rewind import normally performs a full traversal of all
blocks in the pool for verification. If this parameter is set to 0,
the traversal skips non-metadata blocks. It can be toggled once the
import has started to stop or start the traversal of non-metadata blocks.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB1\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.RE
.sp
.ne 2
.na
\fBspa_load_verify_metadata\fR (int)
.ad
.RS 12n
Whether to traverse blocks during an "extreme rewind" (\fB-X\fR)
pool import. Use 0 to disable and 1 to enable.
An extreme rewind import normally performs a full traversal of all
Correct typo in spa_load_verify_metadata docs Signed-off-by: Richard Laager <rlaager@wiktel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4471
2016-03-28 22:13:42 +00:00
blocks in the pool for verification. If this parameter is set to 0,
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
the traversal is not performed. It can be toggled once the import has
started to stop or start the traversal.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB1\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.RE
.sp
.ne 2
.na
spa_load_verify() may consume too much memory When a pool is imported it will scan the pool to verify the integrity of the data and metadata. The amount it scans will depend on the import flags provided. On systems with small amounts of memory or when importing a pool from the crash kernel, it's possible for spa_load_verify to issue too many I/Os that it consumes all the memory of the system resulting in an OOM message or a hang. To prevent this, we limit the amount of memory that the initial pool scan can consume. This change will, by default, use 1/16th of the ARC for scan I/Os to prevent running the system out of memory during import. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: George Wilson george.wilson@delphix.com External-issue: DLPX-65237 External-issue: DLPX-65238 Closes #9146
2019-08-13 14:11:57 +00:00
\fBspa_load_verify_shift\fR (int)
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.ad
.RS 12n
spa_load_verify() may consume too much memory When a pool is imported it will scan the pool to verify the integrity of the data and metadata. The amount it scans will depend on the import flags provided. On systems with small amounts of memory or when importing a pool from the crash kernel, it's possible for spa_load_verify to issue too many I/Os that it consumes all the memory of the system resulting in an OOM message or a hang. To prevent this, we limit the amount of memory that the initial pool scan can consume. This change will, by default, use 1/16th of the ARC for scan I/Os to prevent running the system out of memory during import. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: George Wilson george.wilson@delphix.com External-issue: DLPX-65237 External-issue: DLPX-65238 Closes #9146
2019-08-13 14:11:57 +00:00
Sets the maximum number of bytes to consume during pool import to the log2
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
fraction of the target ARC size.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.sp
spa_load_verify() may consume too much memory When a pool is imported it will scan the pool to verify the integrity of the data and metadata. The amount it scans will depend on the import flags provided. On systems with small amounts of memory or when importing a pool from the crash kernel, it's possible for spa_load_verify to issue too many I/Os that it consumes all the memory of the system resulting in an OOM message or a hang. To prevent this, we limit the amount of memory that the initial pool scan can consume. This change will, by default, use 1/16th of the ARC for scan I/Os to prevent running the system out of memory during import. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: George Wilson george.wilson@delphix.com External-issue: DLPX-65237 External-issue: DLPX-65238 Closes #9146
2019-08-13 14:11:57 +00:00
Default value: \fB4\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 18:58:41 +00:00
.RE
Add spa_slop_shift module option Allow for easy turning of a pools reserved free space. Previous versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity in reserve. Commits 3d45fdd and 0c60cc3 increased this to 1/32. Setting spa_slop_shift=6 will restore the previous default setting. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3724
2015-09-01 16:45:10 +00:00
.sp
.ne 2
.na
\fBspa_slop_shift\fR (int)
.ad
.RS 12n
Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space
in the pool to be consumed. This ensures that we don't run the pool
completely out of space, due to unaccounted changes (e.g. to the MOS).
It also limits the worst-case time to allocate space. If we have
less than this amount of free space, most ZPL operations (e.g. write,
create) will return ENOSPC.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB5\fR.
Add spa_slop_shift module option Allow for easy turning of a pools reserved free space. Previous versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity in reserve. Commits 3d45fdd and 0c60cc3 increased this to 1/32. Setting spa_slop_shift=6 will restore the previous default setting. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3724
2015-09-01 16:45:10 +00:00
.RE
OpenZFS 9486 - reduce memory used by device removal on fragmented pools Device removal allocates a new location for each allocated segment on the disk that's being removed. Each allocation results in one entry in the mapping table, which maps from old location + length to new location. When a fragmented disk is removed, this can result in a large number of mapping entries, and thus a large amount of memory consumed by the mapping table. In the worst real-world cases, we've seen around 1GB of RAM per 1TB of storage removed. We can improve on this situation by allocating larger segments, which span across both allocated and free regions of the device being removed. By including free regions in the allocation (and thus mapping), we reduce the number of mapping entries. For example, if we have a 4K allocation followed by 1K free and then 4K allocated, we would allocate 4+1+4 = 9KB, and then move the entire region (including allocated and free parts). In this case we used one mapping where previously we would have used two, but often the ratio is much higher (up to 20:1 in real-world use). We then need to mark the regions that were free on the removing device as free in the new locations, and also obsolete in the mapping entry. This method preserves the fragmentation of the removing device, rather than consolidating its allocated space into a small number of chunks where possible. But it results in drastic reduction of memory used by the mapping table - around 20x in the most-fragmented cases. In the most fragmented real-world cases, this reduces memory used by the mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less fragmented cases will typically also see around 50-100MB of RAM per 1TB of storage. Porting notes: * Add the following as module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * Document the following module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * zfs_condense_min_mapping_bytes Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9486 OpenZFS-commit: https://github.com/ahrens/illumos/commit/07152e142e44c External-issue: DLPX-57962 Closes #7536
2018-02-26 23:33:55 +00:00
.sp
.ne 2
.na
\fBvdev_removal_max_span\fR (int)
.ad
.RS 12n
During top-level vdev removal, chunks of data are copied from the vdev
which may include free space in order to trade bandwidth for IOPS.
This parameter determines the maximum span of free space (in bytes)
which will be included as "unnecessary" data in a chunk of copied data.
The default value here was chosen to align with
\fBzfs_vdev_read_gap_limit\fR, which is a similar concept when doing
regular reads (but there's no reason it has to be the same).
.sp
Default value: \fB32,768\fR.
.RE
vdev_ashift should only be set once == Motivation and Context The new vdev ashift optimization prevents the removal of devices when a zfs configuration is comprised of disks which have different logical and physical block sizes. This is caused because we set 'spa_min_ashift' in vdev_open and then later call 'vdev_ashift_optimize'. This would result in an inconsistency between spa's ashift calculations and that of the top-level vdev. In addition, the optimization logical ignores the overridden ashift value that would be provided by '-o ashift=<val>'. == Description This change reworks the vdev ashift optimization so that it's only set the first time the device is configured. It still allows the physical and logical ahsift values to be set every time the device is opened but those values are only consulted on first open. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Cedric Berger <cedric@precidata.com> Signed-off-by: George Wilson <gwilson@delphix.com> External-Issue: DLPX-71831 Closes #10932
2020-09-18 19:13:47 +00:00
.sp
.ne 2
.na
\fBvdev_file_logical_ashift\fR (ulong)
.ad
.RS 12n
Logical ashift for file-based devices.
.sp
Default value: \fB9\fR.
.RE
.sp
.ne 2
.na
\fBvdev_file_physical_ashift\fR (ulong)
.ad
.RS 12n
Physical ashift for file-based devices.
.sp
Default value: \fB9\fR.
.RE
fat zap should prefetch when iterating When iterating over a ZAP object, we're almost always certain to iterate over the entire object. If there are multiple leaf blocks, we can realize a performance win by issuing reads for all the leaf blocks in parallel when the iteration begins. For example, if we have 10,000 snapshots, "zfs destroy -nv pool/fs@1%9999" can take 30 minutes when the cache is cold. This change provides a >3x performance improvement, by issuing the reads for all ~64 blocks of each ZAP object in parallel. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-58347 Closes #8862
2019-06-12 20:13:09 +00:00
.sp
.ne 2
.na
\fBzap_iterate_prefetch\fR (int)
.ad
.RS 12n
If this is set, when we start iterating over a ZAP object, zfs will prefetch
the entire object (all leaf blocks). However, this is limited by
\fBdmu_prefetch_max\fR.
.sp
Use \fB1\fR for on (default) and \fB0\fR for off.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfetch_array_rd_sz\fR (ulong)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 12:23:31 +00:00
If prefetching is enabled, disable prefetching for reads larger than this size.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-26 21:10:31 +00:00
\fBzfetch_max_distance\fR (uint)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Expose zfetch_max_idistance tunable FreeBSD had this value tunable before the switch to the new OpenZFS. The tunable name has changed, breaking legacy compat. Restore legacy compat for this tunable, properly expose the tunable with the new name on all platforms, and document it in zfs-module-parameters(5). While here, clean up the documentation for zfetch_max_distance a bit. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #11038
2020-10-13 16:32:34 +00:00
Max bytes to prefetch per stream.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Expose zfetch_max_idistance tunable FreeBSD had this value tunable before the switch to the new OpenZFS. The tunable name has changed, breaking legacy compat. Restore legacy compat for this tunable, properly expose the tunable with the new name on all platforms, and document it in zfs-module-parameters(5). While here, clean up the documentation for zfetch_max_distance a bit. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #11038
2020-10-13 16:32:34 +00:00
Default value: \fB8,388,608\fR (8MB).
.RE
.sp
.ne 2
.na
\fBzfetch_max_idistance\fR (uint)
.ad
.RS 12n
Max bytes to prefetch indirects for per stream.
.sp
Default vaule: \fB67,108,864\fR (64MB).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfetch_max_streams\fR (uint)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 12:23:31 +00:00
Max number of streams per zfetch (prefetch streams per file).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB8\fR.
.RE
.sp
.ne 2
.na
\fBzfetch_min_sec_reap\fR (uint)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 12:23:31 +00:00
Min time before an active prefetch stream can be reclaimed
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB2\fR.
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_abd_scatter_enabled\fR (int)
.ad
.RS 12n
Enables ARC from using scatter/gather lists and forces all allocations to be
linear in kernel memory. Disabling can improve performance in some code paths
at the expense of fragmented kernel memory.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_abd_scatter_max_order\fR (iunt)
.ad
.RS 12n
Maximum number of consecutive memory pages allocated in a single block for
scatter/gather lists. Default value is specified by the kernel itself.
.sp
Default value: \fB10\fR at the time of this writing.
.RE
abd_alloc should use scatter for >1K allocations abd_alloc() normally does scatter allocations, thus solving the problem that ABD originally set out to: the bulk of ZFS's allocations are single pages, which are faster to allocate and free, and don't suffer from internal fragmentation (and the inability to reclaim memory because some buffers in the slab are still allocated). However, the current code does linear allocations for 4KB and smaller allocations, defeating the purpose of ABD. Scatter ABD's use at least one page each, so sub-page allocations waste some space when allocated as scatter (e.g. 2KB scatter allocation wastes half of each page). Using linear ABD's for small allocations means that they will be put on slabs which contain many allocations. This can improve memory efficiency, but it also makes it much harder for ARC evictions to actually free pages, because all the buffers on one slab need to be freed in order for the slab (and underlying pages) to be freed. Typically, 512B and 1KB kmem caches have 16 buffers per slab, so it's possible for them to actually waste more memory than scatter (one page per buf = wasting 3/4 or 7/8th; one buf per slab = wasting 15/16th). Spill blocks are typically 512B and are heavily used on systems running selinux with the default dnode size and the `xattr=sa` property set. By default we will use linear allocations for 512B and 1KB, and scatter allocations for larger (1.5KB and up). Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: DHE <git@dehacked.net> Reviewed-by: Chunwei Chen <tuxoko@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Don Brady <don.brady@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #8455
2019-03-01 01:52:55 +00:00
.sp
.ne 2
.na
\fBzfs_abd_scatter_min_size\fR (uint)
.ad
.RS 12n
This is the minimum allocation size that will use scatter (page-based)
ABD's. Smaller allocations will use linear ABD's.
.sp
Default value: \fB1536\fR (512B and 1KB allocations will be linear).
.RE
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 12:42:40 +00:00
.sp
.ne 2
.na
\fBzfs_arc_dnode_limit\fR (ulong)
.ad
.RS 12n
When the number of bytes consumed by dnodes in the ARC exceeds this number of
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
bytes, try to unpin some of it in response to demand for non-metadata. This
Fix manual description of zfs_arc_dnode_limit In arc_evict_state() we start pruning when arc_dnode_size > arc_dnode_limit, i.e. arc_dnode_limit is a ceiling rather than a floor. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chris Dunlop <chris@onthe.net.au> Closes #6228
2017-06-14 20:23:02 +00:00
value acts as a ceiling to the amount of dnode metadata, and defaults to 0 which
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
indicates that a percent which is based on \fBzfs_arc_dnode_limit_percent\fR of
the ARC meta buffers that may be used for dnodes.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 12:42:40 +00:00
See also \fBzfs_arc_meta_prune\fR which serves a similar purpose but is used
when the amount of metadata in the ARC exceeds \fBzfs_arc_meta_limit\fR rather
than in response to overall demand for non-metadata.
.sp
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_arc_dnode_limit_percent\fR (ulong)
.ad
.RS 12n
Percentage that can be consumed by dnodes of ARC meta buffers.
.sp
See also \fBzfs_arc_dnode_limit\fR which serves a similar purpose but has a
higher priority if set to nonzero value.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB10\fR%.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 12:42:40 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_arc_dnode_reduce_percent\fR (ulong)
.ad
.RS 12n
Percentage of ARC dnodes to try to scan in response to demand for non-metadata
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 01:03:57 +00:00
when the number of bytes consumed by dnodes exceeds \fBzfs_arc_dnode_limit\fR.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 12:42:40 +00:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB10\fR% of the number of dnodes in the ARC.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 12:42:40 +00:00
.RE
Illumos 5034 - ARC's buf_hash_table is too small 5034 ARC's buf_hash_table is too small Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Gordon Ross <gwr@nexenta.com> References: https://www.illumos.org/issues/5034 https://github.com/illumos/illumos-gate/commit/63e911b Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2615
2014-08-20 17:09:40 +00:00
.sp
.ne 2
.na
\fBzfs_arc_average_blocksize\fR (int)
.ad
.RS 12n
The ARC's buffer hash table is sized based on the assumption of an average
block size of \fBzfs_arc_average_blocksize\fR (default 8K). This works out
to roughly 1MB of hash table per 1GB of physical memory with 8-byte pointers.
For configurations with a known larger average block size this value can be
increased to reduce the memory footprint.
.sp
Default value: \fB8192\fR.
.RE
Revise ARC shrinker algorithm The ARC shrinker callback `arc_shrinker_count/_scan()` is invoked by the kernel's shrinker mechanism when the system is running low on free pages. This happens via 2 code paths: 1. "direct reclaim": The system is attempting to allocate a page, but we are low on memory. The ARC shrinker callback is invoked from the page-allocation code path. 2. "indirect reclaim": kswapd notices that there aren't many free pages, so it invokes the ARC shrinker callback. In both cases, the kernel's shrinker code requests that the ARC shrinker callback release some of its cache, and then it measures how many pages were released. However, it's measurement of released pages does not include pages that are freed via `__free_pages()`, which is how the ARC releases memory (via `abd_free_chunks()`). Rather, the kernel shrinker code is looking for pages to be placed on the lists of reclaimable pages (which is separate from actually-free pages). Because the kernel shrinker code doesn't detect that the ARC has released pages, it may call the ARC shrinker callback many times, resulting in the ARC "collapsing" down to `arc_c_min`. This has several negative impacts: 1. ZFS doesn't use RAM to cache data effectively. 2. In the direct reclaim case, a single page allocation may wait a long time (e.g. more than a minute) while we evict the entire ARC. 3. Even with the improvements made in 67c0f0dedc5 ("ARC shrinking blocks reads/writes"), occasionally `arc_size` may stay above `arc_c` for the entire time of the ARC collapse, thus blocking ZFS read/write operations in `arc_get_data_impl()`. To address these issues, this commit limits the ways that the ARC shrinker callback can be used by the kernel shrinker code, and mitigates the impact of arc_is_overflowing() on ZFS read/write operations. With this commit: 1. We limit the amount of data that can be reclaimed from the ARC via the "direct reclaim" shrinker. This limits the amount of time it takes to allocate a single page. 2. We do not allow the ARC to shrink via kswapd (indirect reclaim). Instead we rely on `arc_evict_zthr` to monitor free memory and reduce the ARC target size to keep sufficient free memory in the system. Note that we can't simply rely on limiting the amount that we reclaim at once (as for the direct reclaim case), because kswapd's "boosted" logic can invoke the callback an unlimited number of times (see `balance_pgdat()`). 3. When `arc_is_overflowing()` and we want to allocate memory, `arc_get_data_impl()` will wait only for a multiple of the requested amount of data to be evicted, rather than waiting for the ARC to no longer be overflowing. This allows ZFS reads/writes to make progress even while the ARC is overflowing, while also ensuring that the eviction thread makes progress towards reducing the total amount of memory used by the ARC. 4. The amount of memory that the ARC always tries to keep free for the rest of the system, `arc_sys_free` is increased. 5. Now that the shrinker callback is able to provide feedback to the kernel's shrinker code about our progress, we can safely enable the kswapd hook. This will allow the arc to receive notifications when memory pressure is first detected by the kernel. We also re-enable the appropriate kstats to track these callbacks. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: George Wilson <george.wilson@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10600
2020-08-01 04:10:52 +00:00
.sp
.ne 2
.na
\fBzfs_arc_eviction_pct\fR (int)
.ad
.RS 12n
When \fBarc_is_overflowing()\fR, \fBarc_get_data_impl()\fR waits for this
percent of the requested amount of data to be evicted. For example, by
default for every 2KB that's evicted, 1KB of it may be "reused" by a new
allocation. Since this is above 100%, it ensures that progress is made
towards getting \fBarc_size\fR under \fBarc_c\fR. Since this is finite, it
ensures that allocations can still happen, even during the potentially long
time that \fBarc_size\fR is more than \fBarc_c\fR.
.sp
Default value: \fB200\fR.
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.sp
.ne 2
.na
\fBzfs_arc_evict_batch_limit\fR (int)
.ad
.RS 12n
man: fix spelling mistakes in manual A few minor mistakes than should be fixed: zpool: compatability -> compatibility zfs: accessable -> accessible availible -> available zfs-events: availible -> available zfs-module-parameters: proceding -> proceeding Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3544
2015-07-01 11:42:35 +00:00
Number ARC headers to evict per sub-list before proceeding to another sub-list.
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
This batch-style operation prevents entire sub-lists from being evicted at once
but comes at a cost of additional unlocking and locking.
.sp
Default value: \fB10\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_arc_grow_retry\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
If set to a non zero value, it will replace the arc_grow_retry value with this value.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
The arc_grow_retry value (default 5) is the number of seconds the ARC will wait before
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
trying to resume growth after a memory pressure event.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 18:30:00 +00:00
\fBzfs_arc_lotsfree_percent\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 18:30:00 +00:00
Throttle I/O when free system memory drops below this percentage of total
system memory. Setting this value to 0 will disable the throttle.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB10\fR%.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 18:30:00 +00:00
\fBzfs_arc_max\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Let default arc_c_max be platform dependent Linux changed the default max ARC size to 1/2 of physical memory to deal with shortcomings of the Linux SLUB allocator. Other platforms do not require the same logic. Implement an arc_default_max() function to determine a default max ARC size in platform code. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10155
2020-03-27 16:14:46 +00:00
Max size of ARC in bytes. If set to 0 then the max size of ARC is determined
by the amount of system memory installed. For Linux, 1/2 of system memory will
be used as the limit. For FreeBSD, the larger of all system memory - 1GB or
5/8 of system memory will be used as the limit. This value must be at least
67108864 (64 megabytes).
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
.sp
This value can be changed dynamically with some caveats. It cannot be set back
to 0 while running and reducing it below the current ARC size will not cause
the ARC to shrink without memory pressure to induce shrinking.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 18:30:00 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
.sp
.ne 2
.na
\fBzfs_arc_meta_adjust_restarts\fR (ulong)
.ad
.RS 12n
The number of restart passes to make while scanning the ARC attempting
the free buffers in order to stay below the \fBzfs_arc_meta_limit\fR.
This value should not need to be tuned but is available to facilitate
performance analysis.
.sp
Default value: \fB4096\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_arc_meta_limit\fR (ulong)
.ad
.RS 12n
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:07:47 +00:00
The maximum allowed size in bytes that meta data buffers are allowed to
consume in the ARC. When this limit is reached meta data buffers will
be reclaimed even if the overall arc_c_max has not been reached. This
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
value defaults to 0 which indicates that a percent which is based on
\fBzfs_arc_meta_limit_percent\fR of the ARC may be used for meta data.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
This value my be changed dynamically except that it cannot be set back to 0
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
for a specific percent of the ARC; it must be set to an explicit value.
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
.sp
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
Default value: \fB0\fR.
.RE
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
.sp
.ne 2
.na
\fBzfs_arc_meta_limit_percent\fR (ulong)
.ad
.RS 12n
Percentage of ARC buffers that can be used for meta data.
See also \fBzfs_arc_meta_limit\fR which serves a similar purpose but has a
higher priority if set to nonzero value.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB75\fR%.
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 03:15:37 +00:00
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.sp
.ne 2
.na
\fBzfs_arc_meta_min\fR (ulong)
.ad
.RS 12n
The minimum allowed size in bytes that meta data buffers may consume in
the ARC. This value defaults to 0 which disables a floor on the amount
of the ARC devoted meta data.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_arc_meta_prune\fR (int)
.ad
.RS 12n
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:07:47 +00:00
The number of dentries and inodes to be scanned looking for entries
which can be dropped. This may be required when the ARC reaches the
\fBzfs_arc_meta_limit\fR because dentries and inodes can pin buffers
in the ARC. Increasing this value will cause to dentry and inode caches
to be pruned more aggressively. Setting this value to 0 will disable
pruning the inode and dentry caches.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:07:47 +00:00
Default value: \fB10,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:08:22 +00:00
.sp
.ne 2
.na
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
\fBzfs_arc_meta_strategy\fR (int)
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:08:22 +00:00
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Define the strategy for ARC meta data buffer eviction (meta reclaim strategy).
A value of 0 (META_ONLY) will evict only the ARC meta data buffers.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
A value of 1 (BALANCED) indicates that additional data buffers may be evicted if
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
that is required to in order to evict the required number of meta data buffers.
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:08:22 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB1\fR.
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-17 22:08:22 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_arc_min\fR (ulong)
.ad
.RS 12n
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
Min size of ARC in bytes. If set to 0 then arc_c_min will default to
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
consuming the larger of 32M or 1/32 of total system memory.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_arc_min_prefetch_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Minimum time prefetched blocks are locked in the ARC, specified in ms.
Adjust ARC prefetch tunables to match docs Currently, the ARC exposes 2 tunables (zfs_arc_min_prefetch_ms and zfs_arc_min_prescient_prefetch_ms) which are documented to be specified in milliseconds. However, the code actually uses the values as though they were in seconds. This patch adjusts the code to match the names and documentation of the tunables. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #7126
2018-02-06 00:57:53 +00:00
A value of \fB0\fR will default to 1000 ms.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_arc_min_prescient_prefetch_ms\fR (int)
.ad
.RS 12n
Minimum time "prescient prefetched" blocks are locked in the ARC, specified
Fix typos in man/ Reviewed-by: Ryan Moeller <ryan@ixsystems.com> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Closes #9233
2019-08-30 16:41:35 +00:00
in ms. These blocks are meant to be prefetched fairly aggressively ahead of
Adjust ARC prefetch tunables to match docs Currently, the ARC exposes 2 tunables (zfs_arc_min_prefetch_ms and zfs_arc_min_prescient_prefetch_ms) which are documented to be specified in milliseconds. However, the code actually uses the values as though they were in seconds. This patch adjusts the code to match the names and documentation of the tunables. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #7126
2018-02-06 00:57:53 +00:00
the code that may use them. A value of \fB0\fR will default to 6000 ms.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
OpenZFS 9075 - Improve ZFS pool import/load process and corrupted pool recovery Some work has been done lately to improve the debugability of the ZFS pool load (and import) process. This includes: 7638 Refactor spa_load_impl into several functions 8961 SPA load/import should tell us why it failed 7277 zdb should be able to print zfs_dbgmsg's To iterate on top of that, there's a few changes that were made to make the import process more resilient and crash free. One of the first tasks during the pool load process is to parse a config provided from userland that describes what devices the pool is composed of. A vdev tree is generated from that config, and then all the vdevs are opened. The Meta Object Set (MOS) of the pool is accessed, and several metadata objects that are necessary to load the pool are read. The exact configuration of the pool is also stored inside the MOS. Since the configuration provided from userland is external and might not accurately describe the vdev tree of the pool at the txg that is being loaded, it cannot be relied upon to safely operate the pool. For that reason, the configuration in the MOS is read early on. In the past, the two configurations were compared together and if there was a mismatch then the load process was aborted and an error was returned. The latter was a good way to ensure a pool does not get corrupted, however it made the pool load process needlessly fragile in cases where the vdev configuration changed or the userland configuration was outdated. Since the MOS is stored in 3 copies, the configuration provided by userland doesn't have to be perfect in order to read its contents. Hence, a new approach has been adopted: The pool is first opened with the untrusted userland configuration just so that the real configuration can be read from the MOS. The trusted MOS configuration is then used to generate a new vdev tree and the pool is re-opened. When the pool is opened with an untrusted configuration, writes are disabled to avoid accidentally damaging it. During reads, some sanity checks are performed on block pointers to see if each DVA points to a known vdev; when the configuration is untrusted, instead of panicking the system if those checks fail we simply avoid issuing reads to the invalid DVAs. This new two-step pool load process now allows rewinding pools accross vdev tree changes such as device replacement, addition, etc. Loading a pool from an external config file in a clustering environment also becomes much safer now since the pool will import even if the config is outdated and didn't, for instance, register a recent device addition. With this code in place, it became relatively easy to implement a long-sought-after feature: the ability to import a pool with missing top level (i.e. non-redundant) devices. Note that since this almost guarantees some loss of data, this feature is for now restricted to a read-only import. Porting notes (ZTS): * Fix 'make dist' target in zpool_import * The maximum path length allowed by tar is 99 characters. Several of the new test cases exceeded this limit resulting in them not being included in the tarball. Shorten the names slightly. * Set/get tunables using accessor functions. * Get last synced txg via the "zfs_txg_history" mechanism. * Clear zinject handlers in cleanup for import_cache_device_replaced and import_rewind_device_replaced in order that the zpool can be exported if there is an error. * Increase FILESIZE to 8G in zfs-test.sh to allow for a larger ext4 file system to be created on ZFS_DISK2. Also, there's no need to partition ZFS_DISK2 at all. The partitioning had already been disabled for multipath devices. Among other things, the partitioning steals some space from the ext4 file system, makes it difficult to accurately calculate the paramters to parted and can make some of the tests fail. * Increase FS_SIZE and FILE_SIZE in the zpool_import test configuration now that FILESIZE is larger. * Write more data in order that device evacuation take lonnger in a couple tests. * Use mkdir -p to avoid errors when the directory already exists. * Remove use of sudo in import_rewind_config_changed. Authored by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9075 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/619c0123 Closes #7459
2016-07-22 14:39:36 +00:00
.sp
.ne 2
.na
\fBzfs_max_missing_tvds\fR (int)
.ad
.RS 12n
Number of missing top-level vdevs which will be allowed during
pool import (only in read-only mode).
.sp
Default value: \fB0\fR
.RE
Make zc_nvlist_src_size limit tunable We limit the size of nvlists passed to the kernel so a user cannot make the kernel do an unreasonably large allocation. On FreeBSD this limit was 128 kiB, which turns out to be a bit too small when doing some operations involving a large number of datasets or snapshots, for example replication. Make this limit tunable, with a platform-specific auto default. Linux keeps its limit at KMALLOC_MAX_SIZE. FreeBSD uses 1/4 of the system limit on user wired memory, which allows it to scale depending on system configuration. Reviewed-by: Matt Macy <mmacy@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <freqlabs@FreeBSD.org> Issue #6572 Closes #10706
2020-08-18 16:33:55 +00:00
.sp
.ne 2
.na
\fBzfs_max_nvlist_src_size\fR (ulong)
.ad
.RS 12n
Maximum size in bytes allowed to be passed as zc_nvlist_src_size for ioctls on
/dev/zfs. This prevents a user from causing the kernel to allocate an excessive
amount of memory. When the limit is exceeded, the ioctl fails with EINVAL and a
description of the error is sent to the zfs-dbgmsg log. This parameter should
not need to be touched under normal circumstances. On FreeBSD, the default is
based on the system limit on user wired memory. On Linux, the default is
Linux: increase max nvlist_src size On Linux increase the maximum allowed size of the src nvlist which can be passed to the /dev/zfs ioctl. Originally, this was set to a maximum of KMALLOC_MAX_SIZE (4M) because it was kmalloc'd. Since that time it's been converted to a vmalloc so that's no longer a hard limit, and it's desirable for `zfs send/recv` to allow larger nvlists so more snapshots can be sent at once. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6572 Closes #11638
2021-02-24 17:57:18 +00:00
\fB128MB\fR.
Make zc_nvlist_src_size limit tunable We limit the size of nvlists passed to the kernel so a user cannot make the kernel do an unreasonably large allocation. On FreeBSD this limit was 128 kiB, which turns out to be a bit too small when doing some operations involving a large number of datasets or snapshots, for example replication. Make this limit tunable, with a platform-specific auto default. Linux keeps its limit at KMALLOC_MAX_SIZE. FreeBSD uses 1/4 of the system limit on user wired memory, which allows it to scale depending on system configuration. Reviewed-by: Matt Macy <mmacy@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <freqlabs@FreeBSD.org> Issue #6572 Closes #10706
2020-08-18 16:33:55 +00:00
.sp
Default value: \fB0\fR (kernel decides)
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.sp
.ne 2
.na
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-15 23:49:33 +00:00
\fBzfs_multilist_num_sublists\fR (int)
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.ad
.RS 12n
To allow more fine-grained locking, each ARC state contains a series
of lists for both data and meta data objects. Locking is performed at
the level of these "sub-lists". This parameters controls the number of
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-15 23:49:33 +00:00
sub-lists per ARC state, and also applies to other uses of the
multilist data structure.
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.sp
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-15 23:49:33 +00:00
Default value: \fB4\fR or the number of online CPUs, whichever is greater
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 03:52:19 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_arc_overflow_shift\fR (int)
.ad
.RS 12n
The ARC size is considered to be overflowing if it exceeds the current
ARC target size (arc_c) by a threshold determined by this parameter.
The threshold is calculated as a fraction of arc_c using the formula
"arc_c >> \fBzfs_arc_overflow_shift\fR".
The default value of 8 causes the ARC to be considered to be overflowing
if it exceeds the target size by 1/256th (0.3%) of the target size.
When the ARC is overflowing, new buffer allocations are stalled until
the reclaim thread catches up and the overflow condition no longer exists.
.sp
Default value: \fB8\fR.
.RE
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-26 22:59:23 +00:00
.sp
.ne 2
.na
\fBzfs_arc_p_min_shift\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
If set to a non zero value, this will update arc_p_min_shift (default 4)
with the new value.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
arc_p_min_shift is used to shift of arc_c for calculating both min and max
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
max arc_p
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-26 22:59:23 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB0\fR.
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-26 22:59:23 +00:00
.RE
Disable arc_p adapt dampener by default It's unclear why adjustments to arc_p need to be dampened as they are in arc_adjust. With that said, it's removal significantly improves the arc's ability to "warm up" to a given workload. Thus, I'm disabling by default until its usefulness is better understood. Signed-off-by: Prakash Surya <surya1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #2110
2014-01-03 18:36:26 +00:00
.sp
.ne 2
.na
\fBzfs_arc_p_dampener_disable\fR (int)
.ad
.RS 12n
Disable arc_p adapt dampener
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_arc_shrink_shift\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
If set to a non zero value, this will update arc_shrink_shift (default 7)
with the new value.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Allow scaling of arc in proportion to pagecache When multiple filesystems are in use, memory pressure causes arc_cache to collapse to a minimum. Allow arc_cache to maintain proportional size even when hit rates are disproportionate. We do this only via evictable size from the kernel shrinker, thus it's only in effect under memory pressure. AKAMAI: zfs: CR 3695072 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #6035
2017-03-16 01:34:56 +00:00
.sp
.ne 2
.na
\fBzfs_arc_pc_percent\fR (uint)
.ad
.RS 12n
Percent of pagecache to reclaim arc to
This tunable allows ZFS arc to play more nicely with the kernel's LRU
Persistent L2ARC This commit makes the L2ARC persistent across reboots. We implement a light-weight persistent L2ARC metadata structure that allows L2ARC contents to be recovered after a reboot. This significantly eases the impact a reboot has on read performance on systems with large caches. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Saso Kiselkov <skiselkov@gmail.com> Co-authored-by: Jorgen Lundman <lundman@lundman.net> Co-authored-by: George Amanakis <gamanakis@gmail.com> Ported-by: Yuxuan Shui <yshuiv7@gmail.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #925 Closes #1823 Closes #2672 Closes #3744 Closes #9582
2020-04-10 17:33:35 +00:00
pagecache. It can guarantee that the ARC size won't collapse under scanning
Allow scaling of arc in proportion to pagecache When multiple filesystems are in use, memory pressure causes arc_cache to collapse to a minimum. Allow arc_cache to maintain proportional size even when hit rates are disproportionate. We do this only via evictable size from the kernel shrinker, thus it's only in effect under memory pressure. AKAMAI: zfs: CR 3695072 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #6035
2017-03-16 01:34:56 +00:00
pressure on the pagecache, yet still allows arc to be reclaimed down to
zfs_arc_min if necessary. This value is specified as percent of pagecache
size (as measured by NR_FILE_PAGES) where that percent may exceed 100. This
only operates during memory pressure/reclaim.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB0\fR% (disabled).
Allow scaling of arc in proportion to pagecache When multiple filesystems are in use, memory pressure causes arc_cache to collapse to a minimum. Allow arc_cache to maintain proportional size even when hit rates are disproportionate. We do this only via evictable size from the kernel shrinker, thus it's only in effect under memory pressure. AKAMAI: zfs: CR 3695072 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #6035
2017-03-16 01:34:56 +00:00
.RE
Revise ARC shrinker algorithm The ARC shrinker callback `arc_shrinker_count/_scan()` is invoked by the kernel's shrinker mechanism when the system is running low on free pages. This happens via 2 code paths: 1. "direct reclaim": The system is attempting to allocate a page, but we are low on memory. The ARC shrinker callback is invoked from the page-allocation code path. 2. "indirect reclaim": kswapd notices that there aren't many free pages, so it invokes the ARC shrinker callback. In both cases, the kernel's shrinker code requests that the ARC shrinker callback release some of its cache, and then it measures how many pages were released. However, it's measurement of released pages does not include pages that are freed via `__free_pages()`, which is how the ARC releases memory (via `abd_free_chunks()`). Rather, the kernel shrinker code is looking for pages to be placed on the lists of reclaimable pages (which is separate from actually-free pages). Because the kernel shrinker code doesn't detect that the ARC has released pages, it may call the ARC shrinker callback many times, resulting in the ARC "collapsing" down to `arc_c_min`. This has several negative impacts: 1. ZFS doesn't use RAM to cache data effectively. 2. In the direct reclaim case, a single page allocation may wait a long time (e.g. more than a minute) while we evict the entire ARC. 3. Even with the improvements made in 67c0f0dedc5 ("ARC shrinking blocks reads/writes"), occasionally `arc_size` may stay above `arc_c` for the entire time of the ARC collapse, thus blocking ZFS read/write operations in `arc_get_data_impl()`. To address these issues, this commit limits the ways that the ARC shrinker callback can be used by the kernel shrinker code, and mitigates the impact of arc_is_overflowing() on ZFS read/write operations. With this commit: 1. We limit the amount of data that can be reclaimed from the ARC via the "direct reclaim" shrinker. This limits the amount of time it takes to allocate a single page. 2. We do not allow the ARC to shrink via kswapd (indirect reclaim). Instead we rely on `arc_evict_zthr` to monitor free memory and reduce the ARC target size to keep sufficient free memory in the system. Note that we can't simply rely on limiting the amount that we reclaim at once (as for the direct reclaim case), because kswapd's "boosted" logic can invoke the callback an unlimited number of times (see `balance_pgdat()`). 3. When `arc_is_overflowing()` and we want to allocate memory, `arc_get_data_impl()` will wait only for a multiple of the requested amount of data to be evicted, rather than waiting for the ARC to no longer be overflowing. This allows ZFS reads/writes to make progress even while the ARC is overflowing, while also ensuring that the eviction thread makes progress towards reducing the total amount of memory used by the ARC. 4. The amount of memory that the ARC always tries to keep free for the rest of the system, `arc_sys_free` is increased. 5. Now that the shrinker callback is able to provide feedback to the kernel's shrinker code about our progress, we can safely enable the kswapd hook. This will allow the arc to receive notifications when memory pressure is first detected by the kernel. We also re-enable the appropriate kstats to track these callbacks. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: George Wilson <george.wilson@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10600
2020-08-01 04:10:52 +00:00
.sp
.ne 2
.na
\fBzfs_arc_shrinker_limit\fR (int)
.ad
.RS 12n
This is a limit on how many pages the ARC shrinker makes available for
eviction in response to one page allocation attempt. Note that in
practice, the kernel's shrinker can ask us to evict up to about 4x this
for one allocation attempt.
.sp
The default limit of 10,000 (in practice, 160MB per allocation attempt with
4K pages) limits the amount of time spent attempting to reclaim ARC memory to
less than 100ms per allocation attempt, even with a small average compressed
block size of ~8KB.
.sp
The parameter can be set to 0 (zero) to disable the limit.
.sp
This parameter only applies on Linux.
.sp
Default value: \fB10,000\fR.
.RE
Update arc_available_memory() to check freemem While Linux doesn't provide detailed information about the state of the VM it does provide us total free pages. This information should be incorporated in to the arc_available_memory() calculation rather than solely relying on a signal from direct reclaim. Conceptually this brings arc_available_memory() back in sync with illumos. It is also desirable that the target amount of free memory be tunable on a system. While the default values are expected to work well for most workloads there may be cases where custom values are needed. The zfs_arc_sys_free module option was added for this purpose. zfs_arc_sys_free - The target number of bytes the ARC should leave as free memory on the system. This value can checked in /proc/spl/kstat/zfs/arcstats and setting this module option will override the default value. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-27 20:17:32 +00:00
.sp
.ne 2
.na
\fBzfs_arc_sys_free\fR (ulong)
.ad
.RS 12n
The target number of bytes the ARC should leave as free memory on the system.
Defaults to the larger of 1/64 of physical memory or 512K. Setting this
option to a non-zero value will override the default.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_autoimport_disable\fR (int)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 12:23:31 +00:00
Disable pool import at module load by ignoring the cache file (typically \fB/etc/zfs/zpool.cache\fR).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
align zfs_autoimport_disable manpage with reality The default was changed in #2820. Signed-off-by: cburroughs <chris.burroughs@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3341
2015-04-24 18:03:26 +00:00
Use \fB1\fR for yes (default) and \fB0\fR for no.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 01:34:51 +00:00
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_checksum_events_per_second\fR (uint)
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 01:34:51 +00:00
.ad
.RS 12n
Rate limit checksum events to this many per second. Note that this should
not be set below the zed thresholds (currently 10 checksums over 10 sec)
or else zed may not trigger any action.
.sp
Default value: 20
.RE
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 19:26:32 +00:00
.sp
.ne 2
.na
\fBzfs_commit_timeout_pct\fR (int)
.ad
.RS 12n
This controls the amount of time that a ZIL block (lwb) will remain "open"
when it isn't "full", and it has a thread waiting for it to be committed to
stable storage. The timeout is scaled based on a percentage of the last lwb
latency to avoid significantly impacting the latency of each individual
transaction record (itx).
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB5\fR%.
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 19:26:32 +00:00
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_condense_indirect_commit_entry_delay_ms\fR (int)
.ad
.RS 12n
Vdev indirection layer (used for device removal) sleeps for this many
milliseconds during mapping generation. Intended for use with the test suite
to throttle vdev removal speed.
.sp
Default value: \fB0\fR (no throttle).
.RE
OpenZFS 9486 - reduce memory used by device removal on fragmented pools Device removal allocates a new location for each allocated segment on the disk that's being removed. Each allocation results in one entry in the mapping table, which maps from old location + length to new location. When a fragmented disk is removed, this can result in a large number of mapping entries, and thus a large amount of memory consumed by the mapping table. In the worst real-world cases, we've seen around 1GB of RAM per 1TB of storage removed. We can improve on this situation by allocating larger segments, which span across both allocated and free regions of the device being removed. By including free regions in the allocation (and thus mapping), we reduce the number of mapping entries. For example, if we have a 4K allocation followed by 1K free and then 4K allocated, we would allocate 4+1+4 = 9KB, and then move the entire region (including allocated and free parts). In this case we used one mapping where previously we would have used two, but often the ratio is much higher (up to 20:1 in real-world use). We then need to mark the regions that were free on the removing device as free in the new locations, and also obsolete in the mapping entry. This method preserves the fragmentation of the removing device, rather than consolidating its allocated space into a small number of chunks where possible. But it results in drastic reduction of memory used by the mapping table - around 20x in the most-fragmented cases. In the most fragmented real-world cases, this reduces memory used by the mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less fragmented cases will typically also see around 50-100MB of RAM per 1TB of storage. Porting notes: * Add the following as module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * Document the following module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * zfs_condense_min_mapping_bytes Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9486 OpenZFS-commit: https://github.com/ahrens/illumos/commit/07152e142e44c External-issue: DLPX-57962 Closes #7536
2018-02-26 23:33:55 +00:00
.sp
.ne 2
.na
\fBzfs_condense_indirect_vdevs_enable\fR (int)
.ad
.RS 12n
Enable condensing indirect vdev mappings. When set to a non-zero value,
attempt to condense indirect vdev mappings if the mapping uses more than
\fBzfs_condense_min_mapping_bytes\fR bytes of memory and if the obsolete
space map object uses more than \fBzfs_condense_max_obsolete_bytes\fR
bytes on-disk. The condensing process is an attempt to save memory by
removing obsolete mappings.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_condense_max_obsolete_bytes\fR (ulong)
.ad
.RS 12n
Only attempt to condense indirect vdev mappings if the on-disk size
of the obsolete space map object is greater than this number of bytes
(see \fBfBzfs_condense_indirect_vdevs_enable\fR).
.sp
Default value: \fB1,073,741,824\fR.
.RE
.sp
.ne 2
.na
\fBzfs_condense_min_mapping_bytes\fR (ulong)
.ad
.RS 12n
Minimum size vdev mapping to attempt to condense (see
\fBzfs_condense_indirect_vdevs_enable\fR).
.sp
Default value: \fB131,072\fR.
.RE
Add dbgmsg kstat Internally ZFS keeps a small log to facilitate debugging. By default the log is disabled, to enable it set zfs_dbgmsg_enable=1. The contents of the log can be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to this proc file clears the log. $ echo 1 >/sys/module/zfs/parameters/zfs_dbgmsg_enable $ echo 0 >/proc/spl/kstat/zfs/dbgmsg $ zpool import tank $ cat /proc/spl/kstat/zfs/dbgmsg 1 0 0x01 -1 0 2492357525542 2525836565501 timestamp message 1441141408 spa=tank async request task=1 1441141408 txg 70 open pool version 5000; software version 5000/5; ... 1441141409 spa=tank async request task=32 1441141409 txg 72 import pool version 5000; software version 5000/5; ... 1441141414 command: lt-zpool import tank Note the zfs_dbgmsg() and dprintf() functions are both now mapped to the same log. As mentioned above the kernel debug log can be accessed though the /proc/spl/kstat/zfs/dbgmsg kstat. For user space consumers log messages are immediately written to stdout after applying the ZFS_DEBUG environment variable. $ ZFS_DEBUG=on ./cmd/ztest/ztest -V Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ned Bass <bass6@llnl.gov> Closes #3728
2015-09-01 20:19:10 +00:00
.sp
.ne 2
.na
\fBzfs_dbgmsg_enable\fR (int)
.ad
.RS 12n
Internally ZFS keeps a small log to facilitate debugging. By default the log
is disabled, to enable it set this option to 1. The contents of the log can
be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to
this proc file clears the log.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_dbgmsg_maxsize\fR (int)
.ad
.RS 12n
The maximum size in bytes of the internal ZFS debug log.
.sp
Default value: \fB4M\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_dbuf_state_index\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
This feature is currently unused. It is normally used for controlling what
reporting is available under /proc/spl/kstat/zfs.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_deadman_enabled\fR (int)
.ad
.RS 12n
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-01-31 22:19:08 +00:00
When a pool sync operation takes longer than \fBzfs_deadman_synctime_ms\fR
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
milliseconds, or when an individual I/O takes longer than
\fBzfs_deadman_ziotime_ms\fR milliseconds, then the operation is considered to
be "hung". If \fBzfs_deadman_enabled\fR is set then the deadman behavior is
invoked as described by the \fBzfs_deadman_failmode\fR module option.
By default the deadman is enabled and configured to \fBwait\fR which results
in "hung" I/Os only being logged. The deadman is automatically disabled
when a pool gets suspended.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_deadman_failmode\fR (charp)
.ad
.RS 12n
Controls the failure behavior when the deadman detects a "hung" I/O. Valid
values are \fBwait\fR, \fBcontinue\fR, and \fBpanic\fR.
.sp
\fBwait\fR - Wait for a "hung" I/O to complete. For each "hung" I/O a
"deadman" event will be posted describing that I/O.
.sp
\fBcontinue\fR - Attempt to recover from a "hung" I/O by re-dispatching it
to the I/O pipeline if possible.
.sp
\fBpanic\fR - Panic the system. This can be used to facilitate an automatic
fail-over to a properly configured fail-over partner.
.sp
Default value: \fBwait\fR.
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-01-31 22:19:08 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_deadman_checktime_ms\fR (int)
.ad
.RS 12n
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
Check time in milliseconds. This defines the frequency at which we check
for hung I/O and potentially invoke the \fBzfs_deadman_failmode\fR behavior.
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-01-31 22:19:08 +00:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
Default value: \fB60,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
\fBzfs_deadman_synctime_ms\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-01-31 22:19:08 +00:00
Interval in milliseconds after which the deadman is triggered and also
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
the interval after which a pool sync operation is considered to be "hung".
Once this limit is exceeded the deadman will be invoked every
\fBzfs_deadman_checktime_ms\fR milliseconds until the pool sync completes.
.sp
Default value: \fB600,000\fR.
.RE
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-01-31 22:19:08 +00:00
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
.ne 2
.na
\fBzfs_deadman_ziotime_ms\fR (ulong)
.ad
.RS 12n
Interval in milliseconds after which the deadman is triggered and an
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
individual I/O operation is considered to be "hung". As long as the I/O
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-18 22:06:07 +00:00
remains "hung" the deadman will be invoked every \fBzfs_deadman_checktime_ms\fR
milliseconds until the I/O completes.
.sp
Default value: \fB300,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_dedup_prefetch\fR (int)
.ad
.RS 12n
Enable prefetching dedup-ed blks
.sp
Change the default 'zfs_dedup_prefetch' value to '0' This gives a huge performance improvement in operations with deduped datasets especially when the bottleneck is the amount of ram available for zfs. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2639
2014-08-30 02:13:26 +00:00
Use \fB1\fR for yes and \fB0\fR to disable (default).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBzfs_delay_min_dirty_percent\fR (int)
.ad
.RS 12n
Start to delay each transaction once there is this amount of dirty data,
expressed as a percentage of \fBzfs_dirty_data_max\fR.
This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB60\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_delay_scale\fR (int)
.ad
.RS 12n
This controls how quickly the transaction delay approaches infinity.
Larger values cause longer delays for a given amount of dirty data.
.sp
For the smoothest delay, this value should be about 1 billion divided
by the maximum number of operations per second. This will smoothly
handle between 10x and 1/10th this number.
.sp
See the section "ZFS TRANSACTION DELAY".
.sp
Note: \fBzfs_delay_scale\fR * \fBzfs_dirty_data_max\fR must be < 2^64.
.sp
Default value: \fB500,000\fR.
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_disable_ivset_guid_check\fR (int)
.ad
.RS 12n
Disables requirement for IVset guids to be present and match when doing a raw
receive of encrypted datasets. Intended for users whose pools were created with
Replace ZFS on Linux references with OpenZFS This change updates the documentation to refer to the project as OpenZFS instead ZFS on Linux. Web links have been updated to refer to https://github.com/openzfs/zfs. The extraneous zfsonlinux.org web links in the ZED and SPL sources have been dropped. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #11007
2020-10-09 03:10:13 +00:00
OpenZFS pre-release versions and now have compatibility issues.
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_key_max_salt_uses\fR (ulong)
.ad
.RS 12n
Maximum number of uses of a single salt value before generating a new one for
encrypted datasets. The default value is also the maximum that will be
accepted.
.sp
Default value: \fB400,000,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_object_mutex_size\fR (uint)
.ad
.RS 12n
Size of the znode hashtable used for holds.
Due to the need to hold locks on objects that may not exist yet, kernel mutexes
are not created per-object and instead a hashtable is used where collisions
will result in objects waiting when there is not actually contention on the
same object.
.sp
Default value: \fB64\fR.
.RE
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 01:34:51 +00:00
.sp
.ne 2
.na
Fix typo in update to zfs-module-parameters(5) Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <guss80@gmail.com> Reviewed-by: bunder2015 <omfgbunder@gmail.com> Signed-off-by: Rich Ercolani <rincebrain@gmail.com> Closes #8153
2018-11-26 18:23:58 +00:00
\fBzfs_slow_io_events_per_second\fR (int)
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 01:34:51 +00:00
.ad
.RS 12n
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
Rate limit delay zevents (which report slow I/Os) to this many per second.
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 01:34:51 +00:00
.sp
Default value: 20
.RE
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
.sp
.ne 2
.na
\fBzfs_unflushed_max_mem_amt\fR (ulong)
.ad
.RS 12n
Upper-bound limit for unflushed metadata changes to be held by the
log spacemap in memory (in bytes).
.sp
Default value: \fB1,073,741,824\fR (1GB).
.RE
.sp
.ne 2
.na
\fBzfs_unflushed_max_mem_ppm\fR (ulong)
.ad
.RS 12n
Percentage of the overall system memory that ZFS allows to be used
for unflushed metadata changes by the log spacemap.
(value is calculated over 1000000 for finer granularity).
.sp
Default value: \fB1000\fR (which is divided by 1000000, resulting in
the limit to be \fB0.1\fR% of memory)
.RE
.sp
.ne 2
.na
\fBzfs_unflushed_log_block_max\fR (ulong)
.ad
.RS 12n
Describes the maximum number of log spacemap blocks allowed for each pool.
The default value of 262144 means that the space in all the log spacemaps
can add up to no more than 262144 blocks (which means 32GB of logical
space before compression and ditto blocks, assuming that blocksize is
128k).
.sp
This tunable is important because it involves a trade-off between import
time after an unclean export and the frequency of flushing metaslabs.
The higher this number is, the more log blocks we allow when the pool is
active which means that we flush metaslabs less often and thus decrease
the number of I/Os for spacemap updates per TXG.
At the same time though, that means that in the event of an unclean export,
there will be more log spacemap blocks for us to read, inducing overhead
in the import time of the pool.
The lower the number, the amount of flushing increases destroying log
blocks quicker as they become obsolete faster, which leaves less blocks
to be read during import time after a crash.
.sp
Each log spacemap block existing during pool import leads to approximately
one extra logical I/O issued.
This is the reason why this tunable is exposed in terms of blocks rather
than space used.
.sp
Default value: \fB262144\fR (256K).
.RE
.sp
.ne 2
.na
\fBzfs_unflushed_log_block_min\fR (ulong)
.ad
.RS 12n
If the number of metaslabs is small and our incoming rate is high, we
could get into a situation that we are flushing all our metaslabs every
TXG.
Thus we always allow at least this many log blocks.
.sp
Default value: \fB1000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_unflushed_log_block_pct\fR (ulong)
.ad
.RS 12n
Tunable used to determine the number of blocks that can be used for
the spacemap log, expressed as a percentage of the total number of
metaslabs in the pool.
.sp
Default value: \fB400\fR (read as \fB400\fR% - meaning that the number
of log spacemap blocks are capped at 4 times the number of
metaslabs in the pool).
.RE
port async unlinked drain from illumos-nexenta This patch is an async implementation of the existing sync zfs_unlinked_drain() function. This function is called at mount time and is responsible for freeing znodes that we didn't get to freeing before. We don't have to hold mounting of the dataset until the unlinked list is fully drained as is done now. Since we can process the unlinked set asynchronously this results in a better user experience when mounting a dataset with entries in the unlinked set. Reviewed by: Jorgen Lundman <lundman@lundman.net> Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> Closes #8142
2019-02-12 18:41:15 +00:00
.sp
.ne 2
.na
\fBzfs_unlink_suspend_progress\fR (uint)
.ad
.RS 12n
When enabled, files will not be asynchronously removed from the list of pending
unlinks and the space they consume will be leaked. Once this option has been
disabled and the dataset is remounted, the pending unlinks will be processed
and the freed space returned to the pool.
This option is used by the test suite to facilitate testing.
.sp
Uses \fB0\fR (default) to allow progress and \fB1\fR to pause progress.
.RE
Reintroduce zfs_remove() synchronous deletes Reintroduce a slightly adapted version of the Illumos logic for synchronous unlinks. The basic idea here is that only files smaller than zfs_delete_blocks (20480) blocks should be deleted synchronously. Unlinking larger files should be handled asynchronously to minimize impact to the caller. To accomplish this iput() which is responsible for calling zfs_znode_delete() on Linux is only called in the delete_now path. Otherwise zfs_async_iput() is used which allows the last reference to be dropped by a taskq thread effectively making the removal asynchronous. Porting notes: - Add zfs_delete_blocks module option for performance analysis. The default value is DMU_MAX_DELETEBLKCNT which is the same as upstream. Reducing this value means that smaller files will be unlinked asynchronously like large files. - All occurrences of zfsvfs changes to zsb. Ported-by: KernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-08-21 01:43:10 +00:00
.sp
.ne 2
.na
\fBzfs_delete_blocks\fR (ulong)
.ad
.RS 12n
This is the used to define a large file for the purposes of delete. Files
containing more than \fBzfs_delete_blocks\fR will be deleted asynchronously
while smaller files are deleted synchronously. Decreasing this value will
reduce the time spent in an unlink(2) system call at the expense of a longer
delay before the freed space is available.
.sp
Default value: \fB20,480\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBzfs_dirty_data_max\fR (int)
.ad
.RS 12n
Determines the dirty space limit in bytes. Once this limit is exceeded, new
writes are halted until space frees up. This parameter takes precedence
over \fBzfs_dirty_data_max_percent\fR.
See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB10\fR% of physical RAM, capped at \fBzfs_dirty_data_max_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_max\fR (int)
.ad
.RS 12n
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed in bytes.
This limit is only enforced at module load time, and will be ignored if
\fBzfs_dirty_data_max\fR is later changed. This parameter takes
precedence over \fBzfs_dirty_data_max_max_percent\fR. See the section
"ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB25\fR% of physical RAM.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_max_percent\fR (int)
.ad
.RS 12n
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed as a
percentage of physical RAM. This limit is only enforced at module load
time, and will be ignored if \fBzfs_dirty_data_max\fR is later changed.
The parameter \fBzfs_dirty_data_max_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB25\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_percent\fR (int)
.ad
.RS 12n
Determines the dirty space limit, expressed as a percentage of all
memory. Once this limit is exceeded, new writes are halted until space frees
up. The parameter \fBzfs_dirty_data_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB10\fR%, subject to \fBzfs_dirty_data_max_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-12 23:46:58 +00:00
\fBzfs_dirty_data_sync_percent\fR (int)
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.ad
.RS 12n
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-12 23:46:58 +00:00
Start syncing out a transaction group if there's at least this much dirty data
as a percentage of \fBzfs_dirty_data_max\fR. This should be less than
\fBzfs_vdev_async_write_active_min_dirty_percent\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-12 23:46:58 +00:00
Default value: \fB20\fR% of \fBzfs_dirty_data_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
linux: add basic fallocate(mode=0/2) compatibility Implement semi-compatible functionality for mode=0 (preallocation) and mode=FALLOC_FL_KEEP_SIZE (preallocation beyond EOF) for ZPL. Since ZFS does COW and snapshots, preallocating blocks for a file cannot guarantee that writes to the file will not run out of space. Even if the first overwrite was guaranteed, it would not handle any later overwrite of blocks due to COW, so strict compliance is futile. Instead, make a best-effort check that at least enough free space is currently available in the pool (with a bit of margin), then create a sparse file of the requested size and continue on with life. This does not handle all cases (e.g. several fallocate() calls before writing into the files when the filesystem is nearly full), which would require a more complex mechanism to be implemented, probably based on a modified version of dmu_prealloc(), but is usable as-is. A new module option zfs_fallocate_reserve_percent is used to control the reserve margin for any single fallocate call. By default, this is 110% of the requested preallocation size, so an additional 10% of available space is reserved for overhead to allow the application a good chance of finishing the write when the fallocate() succeeds. If the heuristics of this basic fallocate implementation are not desirable, the old non-functional behavior of returning EOPNOTSUPP for calls can be restored by setting zfs_fallocate_reserve_percent=0. The parameter of zfs_statvfs() is changed to take an inode instead of a dentry, since no dentry is available in zfs_fallocate_common(). A few tests from @behlendorf cover basic fallocate functionality. Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Arshad Hussain <arshad.super@gmail.com> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Co-authored-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andreas Dilger <adilger@dilger.ca> Issue #326 Closes #10408
2020-06-18 18:22:11 +00:00
.sp
.ne 2
.na
\fBzfs_fallocate_reserve_percent\fR (uint)
.ad
.RS 12n
Since ZFS is a copy-on-write filesystem with snapshots, blocks cannot be
preallocated for a file in order to guarantee that later writes will not
run out of space. Instead, fallocate() space preallocation only checks
that sufficient space is currently available in the pool or the user's
project quota allocation, and then creates a sparse file of the requested
size. The requested space is multiplied by \fBzfs_fallocate_reserve_percent\fR
to allow additional space for indirect blocks and other internal metadata.
Setting this value to 0 disables support for fallocate(2) and returns
EOPNOTSUPP for fallocate() space preallocation again.
.sp
Default value: \fB110\fR%
.RE
Implementation of AVX2 optimized Fletcher-4 New functionality: - Preserves existing scalar implementation. - Adds AVX2 optimized Fletcher-4 computation. - Fastest routines selected on module load (benchmark). - Test case for Fletcher-4 added to ztest. New zcommon module parameters: - zfs_fletcher_4_impl (str): selects the implementation to use. "fastest" - use the fastest version available "cycle" - cycle trough all available impl for ztest "scalar" - use the original version "avx2" - new AVX2 implementation if available Performance comparison (Intel i7 CPU, 1MB data buffers): - Scalar: 4216 MB/s - AVX2: 14499 MB/s See contents of `/sys/module/zcommon/parameters/zfs_fletcher_4_impl` to get list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com> Signed-off-by: Andreas Dilger <andreas.dilger@intel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4330
2015-12-09 23:34:16 +00:00
.sp
.ne 2
.na
\fBzfs_fletcher_4_impl\fR (string)
.ad
.RS 12n
Select a fletcher 4 implementation.
.sp
Implementation of SSE optimized Fletcher-4 Builds off of 1eeb4562 (Implementation of AVX2 optimized Fletcher-4) This commit adds another implementation of the Fletcher-4 algorithm. It is automatically selected at module load if it benchmarks higher than all other available implementations. The module benchmark was also amended to analyze the performance of the byteswap-ed version of Fletcher-4, as well as the non-byteswaped version. The average performance of the two is used to select the the fastest implementation available on the host system. Adds a pair of fields to an existing zcommon module parameter: - zfs_fletcher_4_impl (str) "sse2" - new SSE2 implementation if available "ssse3" - new SSSE3 implementation if available Signed-off-by: Tyler J. Stachecki <stachecki.tyler@gmail.com> Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4789
2016-06-24 03:32:40 +00:00
Supported selectors are: \fBfastest\fR, \fBscalar\fR, \fBsse2\fR, \fBssse3\fR,
Add AVX512BW variant of fletcher It is much faster than AVX512F when byteswapping on Skylake-SP and newer, as we can do the byteswap in a single vshufb instead of many instructions. Reviewed by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Chunwei Chen <tuxoko@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net> Closes #9517
2019-10-30 19:26:14 +00:00
\fBavx2\fR, \fBavx512f\fR, \fBavx512bw\fR, and \fBaarch64_neon\fR.
Fletcher4 implementation using avx512f instruction set Algorithm runs 8 parallel sums, consuming 8x uint32_t elements per loop iteration. Size alignment of main fletcher4 methods is adjusted accordingly. New implementation is called 'avx512f'. Note: byteswap method can be implemented more efficiently when avx512bw hardware becomes available. Currently, it is ~ 2x slower than native method. Table shows result of full (native) fletcher4 calculation for different buffer size: fletcher4 4KB 16KB 64KB 128KB 256KB 1MB 16MB -------------------------------------------------------------------- [scalar] 1213 1228 1231 1231 1225 1200 1160 [sse2] 2374 2442 2459 2456 2462 2250 2220 [avx2] 4288 4753 4871 4893 4900 4050 3882 [avx512f] 5975 8445 9196 9221 9262 6307 5620 Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4952
2016-07-06 11:42:04 +00:00
All of the selectors except \fBfastest\fR and \fBscalar\fR require instruction
set extensions to be available and will only appear if ZFS detects that they are
present at runtime. If multiple implementations of fletcher 4 are available,
the \fBfastest\fR will be chosen using a micro benchmark. Selecting \fBscalar\fR
results in the original, CPU based calculation, being used. Selecting any option
other than \fBfastest\fR and \fBscalar\fR results in vector instructions from
the respective CPU instruction set being used.
Implementation of AVX2 optimized Fletcher-4 New functionality: - Preserves existing scalar implementation. - Adds AVX2 optimized Fletcher-4 computation. - Fastest routines selected on module load (benchmark). - Test case for Fletcher-4 added to ztest. New zcommon module parameters: - zfs_fletcher_4_impl (str): selects the implementation to use. "fastest" - use the fastest version available "cycle" - cycle trough all available impl for ztest "scalar" - use the original version "avx2" - new AVX2 implementation if available Performance comparison (Intel i7 CPU, 1MB data buffers): - Scalar: 4216 MB/s - AVX2: 14499 MB/s See contents of `/sys/module/zcommon/parameters/zfs_fletcher_4_impl` to get list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com> Signed-off-by: Andreas Dilger <andreas.dilger@intel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4330
2015-12-09 23:34:16 +00:00
.sp
Default value: \fBfastest\fR.
.RE
Illumos 6251 - add tunable to disable free_bpobj processing 6251 - add tunable to disable free_bpobj processing Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Simon Klinkert <simon.klinkert@gmail.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed by: Albert Lee <trisk@omniti.com> Reviewed by: Xin Li <delphij@freebsd.org> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/6251 https://github.com/illumos/illumos-gate/commit/139510f Porting notes: - Added as module option declaration. - Added to zfs-module-parameters.5 man page. Ported-by: Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2016-01-23 00:41:02 +00:00
.sp
.ne 2
.na
\fBzfs_free_bpobj_enabled\fR (int)
.ad
.RS 12n
Enable/disable the processing of the free_bpobj object.
.sp
Default value: \fB1\fR.
.RE
Illumos 5138 - add tunable for maximum number of blocks freed in one txg Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Mattew Ahrens <mahrens@delphix.com> Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Reviewed by: Richard Elling <richard.elling@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5138 https://github.com/illumos/illumos-gate/commit/af3465d Porting notes: Because support for exposing a uint64_t parameter wasn't added until v3.17-rc1 the zfs_free_max_blocks variable has been declared as a unsigned long. This is already far larger than required and it allows us to avoid additional autoconf compatibility code. The default value has been set to 100,000 on Linux instead of ULONG_MAX which is used on Illumos. This was done to limit the number of outstanding IOs in the system when snapshots are destroyed. This helps ensure individual TXG sync times are kept reasonable and memory isn't wasted managing a huge backlog of outstanding IOs. Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2675 Closes #2581
2014-09-07 15:06:08 +00:00
.sp
.ne 2
.na
OpenZFS 7614, 9064 - zfs device evacuation/removal OpenZFS 7614 - zfs device evacuation/removal OpenZFS 9064 - remove_mirror should wait for device removal to complete This project allows top-level vdevs to be removed from the storage pool with "zpool remove", reducing the total amount of storage in the pool. This operation copies all allocated regions of the device to be removed onto other devices, recording the mapping from old to new location. After the removal is complete, read and free operations to the removed (now "indirect") vdev must be remapped and performed at the new location on disk. The indirect mapping table is kept in memory whenever the pool is loaded, so there is minimal performance overhead when doing operations on the indirect vdev. The size of the in-memory mapping table will be reduced when its entries become "obsolete" because they are no longer used by any block pointers in the pool. An entry becomes obsolete when all the blocks that use it are freed. An entry can also become obsolete when all the snapshots that reference it are deleted, and the block pointers that reference it have been "remapped" in all filesystems/zvols (and clones). Whenever an indirect block is written, all the block pointers in it will be "remapped" to their new (concrete) locations if possible. This process can be accelerated by using the "zfs remap" command to proactively rewrite all indirect blocks that reference indirect (removed) vdevs. Note that when a device is removed, we do not verify the checksum of the data that is copied. This makes the process much faster, but if it were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be possible to copy the wrong data, when we have the correct data on e.g. the other side of the mirror. At the moment, only mirrors and simple top-level vdevs can be removed and no removal is allowed if any of the top-level vdevs are raidz. Porting Notes: * Avoid zero-sized kmem_alloc() in vdev_compact_children(). The device evacuation code adds a dependency that vdev_compact_children() be able to properly empty the vdev_child array by setting it to NULL and zeroing vdev_children. Under Linux, kmem_alloc() and related functions return a sentinel pointer rather than NULL for zero-sized allocations. * Remove comment regarding "mpt" driver where zfs_remove_max_segment is initialized to SPA_MAXBLOCKSIZE. Change zfs_condense_indirect_commit_entry_delay_ticks to zfs_condense_indirect_commit_entry_delay_ms for consistency with most other tunables in which delays are specified in ms. * ZTS changes: Use set_tunable rather than mdb Use zpool sync as appropriate Use sync_pool instead of sync Kill jobs during test_removal_with_operation to allow unmount/export Don't add non-disk names such as "mirror" or "raidz" to $DISKS Use $TEST_BASE_DIR instead of /tmp Increase HZ from 100 to 1000 which is more common on Linux removal_multiple_indirection.ksh Reduce iterations in order to not time out on the code coverage builders. removal_resume_export: Functionally, the test case is correct but there exists a race where the kernel thread hasn't been fully started yet and is not visible. Wait for up to 1 second for the removal thread to be started before giving up on it. Also, increase the amount of data copied in order that the removal not finish before the export has a chance to fail. * MMP compatibility, the concept of concrete versus non-concrete devices has slightly changed the semantics of vdev_writeable(). Update mmp_random_leaf_impl() accordingly. * Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool feature which is not supported by OpenZFS. * Added support for new vdev removal tracepoints. * Test cases removal_with_zdb and removal_condense_export have been intentionally disabled. When run manually they pass as intended, but when running in the automated test environment they produce unreliable results on the latest Fedora release. They may work better once the upstream pool import refectoring is merged into ZoL at which point they will be re-enabled. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Alex Reece <alex@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Richard Laager <rlaager@wiktel.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/7614 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb Closes #6900
2016-09-22 16:30:13 +00:00
\fBzfs_async_block_max_blocks\fR (ulong)
Illumos 5138 - add tunable for maximum number of blocks freed in one txg Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Mattew Ahrens <mahrens@delphix.com> Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Reviewed by: Richard Elling <richard.elling@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5138 https://github.com/illumos/illumos-gate/commit/af3465d Porting notes: Because support for exposing a uint64_t parameter wasn't added until v3.17-rc1 the zfs_free_max_blocks variable has been declared as a unsigned long. This is already far larger than required and it allows us to avoid additional autoconf compatibility code. The default value has been set to 100,000 on Linux instead of ULONG_MAX which is used on Illumos. This was done to limit the number of outstanding IOs in the system when snapshots are destroyed. This helps ensure individual TXG sync times are kept reasonable and memory isn't wasted managing a huge backlog of outstanding IOs. Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2675 Closes #2581
2014-09-07 15:06:08 +00:00
.ad
.RS 12n
Maximum number of blocks freed in a single txg.
.sp
Remove limit on number of async zio_frees of non-dedup blocks The module parameter zfs_async_block_max_blocks limits the number of blocks that can be freed by the background freeing of filesystems and snapshots (from "zfs destroy"), in one TXG. This is useful when freeing dedup blocks, becuase each zio_free() of a dedup block can require an i/o to read the relevant part of the dedup table (DDT), and will also dirty that block. zfs_async_block_max_blocks is set to 100,000 by default. For the more typical case where dedup is not used, this can have a negative performance impact on the rate of background freeing (from "zfs destroy"). For example, with recordsize=8k, and TXG's syncing once every 5 seconds, we can free only 160MB of data per second, which may be much less than the rate we can write data. This change increases zfs_async_block_max_blocks to be unlimited by default. To address the dedup freeing issue, a new tunable is introduced, zfs_max_async_dedup_frees, which limits the number of zio_free()'s of dedup blocks done by background destroys, per txg. The default is 100,000 free's (same as the old zfs_async_block_max_blocks default). Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10000
2020-02-14 16:39:46 +00:00
Default value: \fBULONG_MAX\fR (unlimited).
.RE
.sp
.ne 2
.na
\fBzfs_max_async_dedup_frees\fR (ulong)
.ad
.RS 12n
Maximum number of dedup blocks freed in a single txg.
.sp
Illumos 5138 - add tunable for maximum number of blocks freed in one txg Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Mattew Ahrens <mahrens@delphix.com> Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Reviewed by: Richard Elling <richard.elling@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5138 https://github.com/illumos/illumos-gate/commit/af3465d Porting notes: Because support for exposing a uint64_t parameter wasn't added until v3.17-rc1 the zfs_free_max_blocks variable has been declared as a unsigned long. This is already far larger than required and it allows us to avoid additional autoconf compatibility code. The default value has been set to 100,000 on Linux instead of ULONG_MAX which is used on Illumos. This was done to limit the number of outstanding IOs in the system when snapshots are destroyed. This helps ensure individual TXG sync times are kept reasonable and memory isn't wasted managing a huge backlog of outstanding IOs. Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2675 Closes #2581
2014-09-07 15:06:08 +00:00
Default value: \fB100,000\fR.
.RE
OpenZFS 9256 - zfs send space estimation off by > 10% on some datasets Authored by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> Porting Notes: * Added tuning to man page. * Test case changes dropped, default behavior unchanged. OpenZFS-issue: https://www.illumos.org/issues/9256 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/32356b3c56 Closes #7470
2016-08-26 18:43:21 +00:00
.sp
.ne 2
.na
\fBzfs_override_estimate_recordsize\fR (ulong)
.ad
.RS 12n
Record size calculation override for zfs send estimates.
.sp
Default value: \fB0\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_async_read_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Maximum asynchronous read I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB3\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_read_min_active\fR (int)
.ad
.RS 12n
Minimum asynchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_active_max_dirty_percent\fR (int)
.ad
.RS 12n
When the pool has more than
\fBzfs_vdev_async_write_active_max_dirty_percent\fR dirty data, use
\fBzfs_vdev_async_write_max_active\fR to limit active async writes. If
the dirty data is between min and max, the active I/O limit is linearly
interpolated. See the section "ZFS I/O SCHEDULER".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB60\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_active_min_dirty_percent\fR (int)
.ad
.RS 12n
When the pool has less than
\fBzfs_vdev_async_write_active_min_dirty_percent\fR dirty data, use
\fBzfs_vdev_async_write_min_active\fR to limit active async writes. If
the dirty data is between min and max, the active I/O limit is linearly
interpolated. See the section "ZFS I/O SCHEDULER".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB30\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Maximum asynchronous write I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_min_active\fR (int)
.ad
.RS 12n
Minimum asynchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Increase zfs_vdev_async_write_min_active to 2 Resilver operations frequently cause only a small amount of dirty data to be written to disk at a time, resulting in the IO scheduler to only issue 1 write at a time to the resilvering disk. When it is rotational media the drive will often travel past the next sector to be written before receiving a write command from ZFS, significantly delaying the write of the next sector. Raise zfs_vdev_async_write_min_active so that drives are kept fed during resilvering. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Issue #4825 Closes #5926
2017-03-26 02:36:28 +00:00
Lower values are associated with better latency on rotational media but poorer
resilver performance. The default value of 2 was chosen as a compromise. A
value of 3 has been shown to improve resilver performance further at a cost of
further increasing latency.
.sp
Default value: \fB2\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.RE
OpenZFS 9102 - zfs should be able to initialize storage devices PROBLEM ======== The first access to a block incurs a performance penalty on some platforms (e.g. AWS's EBS, VMware VMDKs). Therefore we recommend that volumes are "thick provisioned", where supported by the platform (VMware). This can create a large delay in getting a new virtual machines up and running (or adding storage to an existing Engine). If the thick provision step is omitted, write performance will be suboptimal until all blocks on the LUN have been written. SOLUTION ========= This feature introduces a way to 'initialize' the disks at install or in the background to make sure we don't incur this first read penalty. When an entire LUN is added to ZFS, we make all space available immediately, and allow ZFS to find unallocated space and zero it out. This works with concurrent writes to arbitrary offsets, ensuring that we don't zero out something that has been (or is in the middle of being) written. This scheme can also be applied to existing pools (affecting only free regions on the vdev). Detailed design: - new subcommand:zpool initialize [-cs] <pool> [<vdev> ...] - start, suspend, or cancel initialization - Creates new open-context thread for each vdev - Thread iterates through all metaslabs in this vdev - Each metaslab: - select a metaslab - load the metaslab - mark the metaslab as being zeroed - walk all free ranges within that metaslab and translate them to ranges on the leaf vdev - issue a "zeroing" I/O on the leaf vdev that corresponds to a free range on the metaslab we're working on - continue until all free ranges for this metaslab have been "zeroed" - reset/unmark the metaslab being zeroed - if more metaslabs exist, then repeat above tasks. - if no more metaslabs, then we're done. - progress for the initialization is stored on-disk in the vdev’s leaf zap object. The following information is stored: - the last offset that has been initialized - the state of the initialization process (i.e. active, suspended, or canceled) - the start time for the initialization - progress is reported via the zpool status command and shows information for each of the vdevs that are initializing Porting notes: - Added zfs_initialize_value module parameter to set the pattern written by "zpool initialize". - Added zfs_vdev_{initializing,removal}_{min,max}_active module options. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: John Wren Kennedy <john.kennedy@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: loli10K <ezomori.nozomu@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Signed-off-by: Tim Chase <tim@chase2k.com> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/9102 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c3963210eb Closes #8230
2018-12-19 14:54:59 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_initializing_max_active\fR (int)
.ad
.RS 12n
Maximum initializing I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_initializing_min_active\fR (int)
.ad
.RS 12n
Minimum initializing I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_max_active\fR (int)
.ad
.RS 12n
The maximum number of I/Os active to each device. Ideally, this will be >=
Reduce latency effects of non-interactive I/O Investigating influence of scrub (especially sequential) on random read latency I've noticed that on some HDDs single 4KB read may take up to 4 seconds! Deeper investigation shown that many HDDs heavily prioritize sequential reads even when those are submitted with queue depth of 1. This patch addresses the latency from two sides: - by using _min_active queue depths for non-interactive requests while the interactive request(s) are active and few requests after; - by throttling it further if no interactive requests has completed while configured amount of non-interactive did. While there, I've also modified vdev_queue_class_to_issue() to give more chances to schedule at least _min_active requests to the lowest priorities. It should reduce starvation if several non-interactive processes are running same time with some interactive and I think should make possible setting of zfs_vdev_max_active to as low as 1. I've benchmarked this change with 4KB random reads from ZVOL with 16KB block size on newly written non-fragmented pool. On fragmented pool I also saw improvements, but not so dramatic. Below are log2 histograms of the random read latency in milliseconds for different devices: 4 2x mirror vdevs of SATA HDD WDC WD20EFRX-68EUZN0 before: 0, 0, 2, 1, 12, 21, 19, 18, 10, 15, 17, 21 after: 0, 0, 0, 24, 101, 195, 419, 250, 47, 4, 0, 0 , that means maximum latency reduction from 2s to 500ms. 4 2x mirror vdevs of SATA HDD WDC WD80EFZX-68UW8N0 before: 0, 0, 2, 31, 38, 28, 18, 12, 17, 20, 24, 10, 3 after: 0, 0, 55, 247, 455, 470, 412, 181, 36, 0, 0, 0, 0 , i.e. from 4s to 250ms. 1 SAS HDD SEAGATE ST14000NM0048 before: 0, 0, 29, 70, 107, 45, 27, 1, 0, 0, 1, 4, 19 after: 1, 29, 681, 1261, 676, 1633, 67, 1, 0, 0, 0, 0, 0 , i.e. from 4s to 125ms. 1 SAS SSD SEAGATE XS3840TE70014 before (microseconds): 0, 0, 0, 0, 0, 0, 0, 0, 70, 18343, 82548, 618 after: 0, 0, 0, 0, 0, 0, 0, 0, 283, 92351, 34844, 90 I've also measured scrub time during the test and on idle pools. On idle fragmented pool I've measured scrub getting few percent faster due to use of QD3 instead of QD2 before. On idle non-fragmented pool I've measured no difference. On busy non-fragmented pool I've measured scrub time increase about 1.5-1.7x, while IOPS increase reached 5-9x. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored-By: iXsystems, Inc. Closes #11166
2020-11-24 17:26:42 +00:00
the sum of each queue's max_active. See the section "ZFS I/O SCHEDULER".
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
Default value: \fB1,000\fR.
.RE
Add device rebuild feature The device_rebuild feature enables sequential reconstruction when resilvering. Mirror vdevs can be rebuilt in LBA order which may more quickly restore redundancy depending on the pools average block size, overall fragmentation and the performance characteristics of the devices. However, block checksums cannot be verified as part of the rebuild thus a scrub is automatically started after the sequential resilver completes. The new '-s' option has been added to the `zpool attach` and `zpool replace` command to request sequential reconstruction instead of healing reconstruction when resilvering. zpool attach -s <pool> <existing vdev> <new vdev> zpool replace -s <pool> <old vdev> <new vdev> The `zpool status` output has been updated to report the progress of sequential resilvering in the same way as healing resilvering. The one notable difference is that multiple sequential resilvers may be in progress as long as they're operating on different top-level vdevs. The `zpool wait -t resilver` command was extended to wait on sequential resilvers. From this perspective they are no different than healing resilvers. Sequential resilvers cannot be supported for RAIDZ, but are compatible with the dRAID feature being developed. As part of this change the resilver_restart_* tests were moved in to the functional/replacement directory. Additionally, the replacement tests were renamed and extended to verify both resilvering and rebuilding. Original-patch-by: Isaac Huang <he.huang@intel.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: John Poduska <jpoduska@datto.com> Co-authored-by: Mark Maybee <mmaybee@cray.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #10349
2020-07-03 18:05:50 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_rebuild_max_active\fR (int)
.ad
.RS 12n
Maximum sequential resilver I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB3\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_rebuild_min_active\fR (int)
.ad
.RS 12n
Minimum sequential resilver I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
OpenZFS 9102 - zfs should be able to initialize storage devices PROBLEM ======== The first access to a block incurs a performance penalty on some platforms (e.g. AWS's EBS, VMware VMDKs). Therefore we recommend that volumes are "thick provisioned", where supported by the platform (VMware). This can create a large delay in getting a new virtual machines up and running (or adding storage to an existing Engine). If the thick provision step is omitted, write performance will be suboptimal until all blocks on the LUN have been written. SOLUTION ========= This feature introduces a way to 'initialize' the disks at install or in the background to make sure we don't incur this first read penalty. When an entire LUN is added to ZFS, we make all space available immediately, and allow ZFS to find unallocated space and zero it out. This works with concurrent writes to arbitrary offsets, ensuring that we don't zero out something that has been (or is in the middle of being) written. This scheme can also be applied to existing pools (affecting only free regions on the vdev). Detailed design: - new subcommand:zpool initialize [-cs] <pool> [<vdev> ...] - start, suspend, or cancel initialization - Creates new open-context thread for each vdev - Thread iterates through all metaslabs in this vdev - Each metaslab: - select a metaslab - load the metaslab - mark the metaslab as being zeroed - walk all free ranges within that metaslab and translate them to ranges on the leaf vdev - issue a "zeroing" I/O on the leaf vdev that corresponds to a free range on the metaslab we're working on - continue until all free ranges for this metaslab have been "zeroed" - reset/unmark the metaslab being zeroed - if more metaslabs exist, then repeat above tasks. - if no more metaslabs, then we're done. - progress for the initialization is stored on-disk in the vdev’s leaf zap object. The following information is stored: - the last offset that has been initialized - the state of the initialization process (i.e. active, suspended, or canceled) - the start time for the initialization - progress is reported via the zpool status command and shows information for each of the vdevs that are initializing Porting notes: - Added zfs_initialize_value module parameter to set the pattern written by "zpool initialize". - Added zfs_vdev_{initializing,removal}_{min,max}_active module options. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: John Wren Kennedy <john.kennedy@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: loli10K <ezomori.nozomu@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Signed-off-by: Tim Chase <tim@chase2k.com> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/9102 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c3963210eb Closes #8230
2018-12-19 14:54:59 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_removal_max_active\fR (int)
.ad
.RS 12n
Maximum removal I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_removal_min_active\fR (int)
.ad
.RS 12n
Minimum removal I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_scrub_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Maximum scrub I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_scrub_min_active\fR (int)
.ad
.RS 12n
Minimum scrub I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_read_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Maximum synchronous read I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_read_min_active\fR (int)
.ad
.RS 12n
Minimum synchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_write_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Maximum synchronous write I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_write_min_active\fR (int)
.ad
.RS 12n
Minimum synchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_trim_max_active\fR (int)
.ad
.RS 12n
Maximum trim/discard I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_trim_min_active\fR (int)
.ad
.RS 12n
Minimum trim/discard I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
Reduce latency effects of non-interactive I/O Investigating influence of scrub (especially sequential) on random read latency I've noticed that on some HDDs single 4KB read may take up to 4 seconds! Deeper investigation shown that many HDDs heavily prioritize sequential reads even when those are submitted with queue depth of 1. This patch addresses the latency from two sides: - by using _min_active queue depths for non-interactive requests while the interactive request(s) are active and few requests after; - by throttling it further if no interactive requests has completed while configured amount of non-interactive did. While there, I've also modified vdev_queue_class_to_issue() to give more chances to schedule at least _min_active requests to the lowest priorities. It should reduce starvation if several non-interactive processes are running same time with some interactive and I think should make possible setting of zfs_vdev_max_active to as low as 1. I've benchmarked this change with 4KB random reads from ZVOL with 16KB block size on newly written non-fragmented pool. On fragmented pool I also saw improvements, but not so dramatic. Below are log2 histograms of the random read latency in milliseconds for different devices: 4 2x mirror vdevs of SATA HDD WDC WD20EFRX-68EUZN0 before: 0, 0, 2, 1, 12, 21, 19, 18, 10, 15, 17, 21 after: 0, 0, 0, 24, 101, 195, 419, 250, 47, 4, 0, 0 , that means maximum latency reduction from 2s to 500ms. 4 2x mirror vdevs of SATA HDD WDC WD80EFZX-68UW8N0 before: 0, 0, 2, 31, 38, 28, 18, 12, 17, 20, 24, 10, 3 after: 0, 0, 55, 247, 455, 470, 412, 181, 36, 0, 0, 0, 0 , i.e. from 4s to 250ms. 1 SAS HDD SEAGATE ST14000NM0048 before: 0, 0, 29, 70, 107, 45, 27, 1, 0, 0, 1, 4, 19 after: 1, 29, 681, 1261, 676, 1633, 67, 1, 0, 0, 0, 0, 0 , i.e. from 4s to 125ms. 1 SAS SSD SEAGATE XS3840TE70014 before (microseconds): 0, 0, 0, 0, 0, 0, 0, 0, 70, 18343, 82548, 618 after: 0, 0, 0, 0, 0, 0, 0, 0, 283, 92351, 34844, 90 I've also measured scrub time during the test and on idle pools. On idle fragmented pool I've measured scrub getting few percent faster due to use of QD3 instead of QD2 before. On idle non-fragmented pool I've measured no difference. On busy non-fragmented pool I've measured scrub time increase about 1.5-1.7x, while IOPS increase reached 5-9x. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored-By: iXsystems, Inc. Closes #11166
2020-11-24 17:26:42 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_nia_delay\fR (int)
.ad
.RS 12n
For non-interactive I/O (scrub, resilver, removal, initialize and rebuild),
the number of concurrently-active I/O's is limited to *_min_active, unless
the vdev is "idle". When there are no interactive I/Os active (sync or
async), and zfs_vdev_nia_delay I/Os have completed since the last
interactive I/O, then the vdev is considered to be "idle", and the number
of concurrently-active non-interactive I/O's is increased to *_max_active.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_nia_credit\fR (int)
.ad
.RS 12n
Some HDDs tend to prioritize sequential I/O so high, that concurrent
random I/O latency reaches several seconds. On some HDDs it happens
even if sequential I/Os are submitted one at a time, and so setting
*_max_active to 1 does not help. To prevent non-interactive I/Os, like
scrub, from monopolizing the device no more than zfs_vdev_nia_credit
I/Os can be sent while there are outstanding incomplete interactive
I/Os. This enforced wait ensures the HDD services the interactive I/O
within a reasonable amount of time.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB5\fR.
.RE
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_queue_depth_pct\fR (int)
.ad
.RS 12n
Update documentation for zfs_vdev_queue_depth_pct It was documented as being related to zfs_vdev_async_max_active when it is actually related to zfs_vdev_async_write_max_active. Also, expand the documentation to describe the allocation throttle which was introduced as part of OpenZFS 7090 in 3dfb57a. Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #6064
2017-04-25 04:01:04 +00:00
Maximum number of queued allocations per top-level vdev expressed as
a percentage of \fBzfs_vdev_async_write_max_active\fR which allows the
system to detect devices that are more capable of handling allocations
and to allocate more blocks to those devices. It allows for dynamic
allocation distribution when devices are imbalanced as fuller devices
will tend to be slower than empty devices.
See also \fBzio_dva_throttle_enabled\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB1000\fR%.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_expire_snapshot\fR (int)
.ad
.RS 12n
Seconds to expire .zfs/snapshot
.sp
Default value: \fB300\fR.
.RE
Support accessing .zfs/snapshot via NFS This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2797 Closes #1655 Closes #616
2015-08-28 21:54:32 +00:00
.sp
.ne 2
.na
\fBzfs_admin_snapshot\fR (int)
.ad
.RS 12n
Allow the creation, removal, or renaming of entries in the .zfs/snapshot
directory to cause the creation, destruction, or renaming of snapshots.
When enabled this functionality works both locally and over NFS exports
which have the 'no_root_squash' option set. This functionality is disabled
by default.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_flags\fR (int)
.ad
.RS 12n
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 00:54:43 +00:00
Set additional debugging flags. The following flags may be bitwise-or'd
together.
.sp
.TS
box;
rB lB
lB lB
r l.
Value Symbolic Name
Description
_
1 ZFS_DEBUG_DPRINTF
Enable dprintf entries in the debug log.
_
2 ZFS_DEBUG_DBUF_VERIFY *
Enable extra dbuf verifications.
_
4 ZFS_DEBUG_DNODE_VERIFY *
Enable extra dnode verifications.
_
8 ZFS_DEBUG_SNAPNAMES
Enable snapshot name verification.
_
16 ZFS_DEBUG_MODIFY
Check for illegally modified ARC buffers.
_
64 ZFS_DEBUG_ZIO_FREE
Enable verification of block frees.
_
128 ZFS_DEBUG_HISTOGRAM_VERIFY
Enable extra spacemap histogram verifications.
Add line info and SET_ERROR() to ZFS debug log Redefine the SET_ERROR macro in terms of __dprintf() so the error return codes get logged as both tracepoint events (if tracepoints are enabled) and as ZFS debug log entries. This also allows us to use the same definition of SET_ERROR() in kernel and user space. Define a new debug flag ZFS_DEBUG_SET_ERROR=512 that may be bitwise or'd into zfs_flags. Setting this flag enables both dprintf() and SET_ERROR() messages in the debug log. That is, setting ZFS_DEBUG_SET_ERROR and ZFS_DEBUG_DPRINTF|ZFS_DEBUG_SET_ERROR are equivalent (this was done for sake of simplicity). Leaving ZFS_DEBUG_SET_ERROR unset suppresses the SET_ERROR() messages which helps avoid cluttering up the logs. To enable SET_ERROR() logging, run: echo 1 > /sys/module/zfs/parameters/zfs_dbgmsg_enable echo 512 > /sys/module/zfs/parameters/zfs_flags Remove the zfs_set_error_class tracepoints event class since SET_ERROR() now uses __dprintf(). This sacrifices a bit of granularity when selecting individual tracepoint events to enable but it makes the code simpler. Include file, function, and line number information in debug log entries. The information is now added to the message buffer in __dprintf() and as a result the zfs_dprintf_class tracepoints event class was changed from a 4 parameter interface to a single parameter. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ned Bass <bass6@llnl.gov> Closes #6400
2017-07-26 06:09:48 +00:00
_
256 ZFS_DEBUG_METASLAB_VERIFY
Verify space accounting on disk matches in-core range_trees.
_
512 ZFS_DEBUG_SET_ERROR
Enable SET_ERROR and dprintf entries in the debug log.
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
_
1024 ZFS_DEBUG_INDIRECT_REMAP
Verify split blocks created by device removal.
_
2048 ZFS_DEBUG_TRIM
Verify TRIM ranges are always within the allocatable range tree.
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
_
4096 ZFS_DEBUG_LOG_SPACEMAP
Verify that the log summary is consistent with the spacemap log
and enable zfs_dbgmsgs for metaslab loading and flushing.
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 00:54:43 +00:00
.TE
.sp
* Requires debug build.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 00:54:43 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Illumos 4390 - I/O errors can corrupt space map when deleting fs/vol 4390 i/o errors when deleting filesystem/zvol can lead to space map corruption Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/4390 https://github.com/illumos/illumos-gate/commit/7fd05ac Porting notes: Previous stack-reduction efforts in traverse_visitb() caused a fair number of un-mergable pieces of code. This patch should reduce its stack footprint a bit more. The new local bptree_entry_phys_t in bptree_add() is dynamically-allocated using kmem_zalloc() for the purpose of stack reduction. The new global zfs_free_leak_on_eio has been defined as an integer rather than a boolean_t as was the case with the related zfs_recover global. Also, zfs_free_leak_on_eio's definition has been inserted into zfs_debug.c for consistency with the existing definition of zfs_recover. Illumos placed it in spa_misc.c. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2545
2014-06-05 21:20:08 +00:00
.sp
.ne 2
.na
\fBzfs_free_leak_on_eio\fR (int)
.ad
.RS 12n
If destroy encounters an EIO while reading metadata (e.g. indirect
blocks), space referenced by the missing metadata can not be freed.
Normally this causes the background destroy to become "stalled", as
it is unable to make forward progress. While in this stalled state,
all remaining space to free from the error-encountering filesystem is
"temporarily leaked". Set this flag to cause it to ignore the EIO,
permanently leak the space from indirect blocks that can not be read,
and continue to free everything else that it can.
The default, "stalling" behavior is useful if the storage partially
fails (i.e. some but not all i/os fail), and then later recovers. In
this case, we will be able to continue pool operations while it is
partially failed, and when it recovers, we can continue to free the
space, with no leaks. However, note that this case is actually
fairly rare.
Typically pools either (a) fail completely (but perhaps temporarily,
e.g. a top-level vdev going offline), or (b) have localized,
permanent errors (e.g. disk returns the wrong data due to bit flip or
firmware bug). In case (a), this setting does not matter because the
pool will be suspended and the sync thread will not be able to make
forward progress regardless. In case (b), because the error is
permanent, the best we can do is leak the minimum amount of space,
which is what setting this flag will do. Therefore, it is reasonable
for this flag to normally be set, but we chose the more conservative
approach of not setting it, so that there is no possibility of
leaking space in the "partial temporary" failure case.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_free_min_time_ms\fR (int)
.ad
.RS 12n
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 01:03:57 +00:00
During a \fBzfs destroy\fR operation using \fBfeature@async_destroy\fR a minimum
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
of this much time will be spent working on freeing blocks per txg.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB1,000\fR.
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_obsolete_min_time_ms\fR (int)
.ad
.RS 12n
Fix typos Correct various typos in the comments and tests. Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Closes #10423
2020-06-10 04:24:09 +00:00
Similar to \fBzfs_free_min_time_ms\fR but for cleanup of old indirection records
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
for removed vdevs.
.sp
Default value: \fB500\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_immediate_write_sz\fR (long)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Largest data block to write to zil. Larger blocks will be treated as if the
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 01:03:57 +00:00
dataset being written to had the property setting \fBlogbias=throughput\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB32,768\fR.
.RE
OpenZFS 9102 - zfs should be able to initialize storage devices PROBLEM ======== The first access to a block incurs a performance penalty on some platforms (e.g. AWS's EBS, VMware VMDKs). Therefore we recommend that volumes are "thick provisioned", where supported by the platform (VMware). This can create a large delay in getting a new virtual machines up and running (or adding storage to an existing Engine). If the thick provision step is omitted, write performance will be suboptimal until all blocks on the LUN have been written. SOLUTION ========= This feature introduces a way to 'initialize' the disks at install or in the background to make sure we don't incur this first read penalty. When an entire LUN is added to ZFS, we make all space available immediately, and allow ZFS to find unallocated space and zero it out. This works with concurrent writes to arbitrary offsets, ensuring that we don't zero out something that has been (or is in the middle of being) written. This scheme can also be applied to existing pools (affecting only free regions on the vdev). Detailed design: - new subcommand:zpool initialize [-cs] <pool> [<vdev> ...] - start, suspend, or cancel initialization - Creates new open-context thread for each vdev - Thread iterates through all metaslabs in this vdev - Each metaslab: - select a metaslab - load the metaslab - mark the metaslab as being zeroed - walk all free ranges within that metaslab and translate them to ranges on the leaf vdev - issue a "zeroing" I/O on the leaf vdev that corresponds to a free range on the metaslab we're working on - continue until all free ranges for this metaslab have been "zeroed" - reset/unmark the metaslab being zeroed - if more metaslabs exist, then repeat above tasks. - if no more metaslabs, then we're done. - progress for the initialization is stored on-disk in the vdev’s leaf zap object. The following information is stored: - the last offset that has been initialized - the state of the initialization process (i.e. active, suspended, or canceled) - the start time for the initialization - progress is reported via the zpool status command and shows information for each of the vdevs that are initializing Porting notes: - Added zfs_initialize_value module parameter to set the pattern written by "zpool initialize". - Added zfs_vdev_{initializing,removal}_{min,max}_active module options. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: John Wren Kennedy <john.kennedy@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: loli10K <ezomori.nozomu@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Signed-off-by: Tim Chase <tim@chase2k.com> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/9102 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c3963210eb Closes #8230
2018-12-19 14:54:59 +00:00
.sp
.ne 2
.na
\fBzfs_initialize_value\fR (ulong)
.ad
.RS 12n
Pattern written to vdev free space by \fBzpool initialize\fR.
.sp
Default value: \fB16,045,690,984,833,335,022\fR (0xdeadbeefdeadbeee).
.RE
Add subcommand to wait for background zfs activity to complete Currently the best way to wait for the completion of a long-running operation in a pool, like a scrub or device removal, is to poll 'zpool status' and parse its output, which is neither efficient nor convenient. This change adds a 'wait' subcommand to the zpool command. When invoked, 'zpool wait' will block until a specified type of background activity completes. Currently, this subcommand can wait for any of the following: - Scrubs or resilvers to complete - Devices to initialized - Devices to be replaced - Devices to be removed - Checkpoints to be discarded - Background freeing to complete For example, a scrub that is in progress could be waited for by running zpool wait -t scrub <pool> This also adds a -w flag to the attach, checkpoint, initialize, replace, remove, and scrub subcommands. When used, this flag makes the operations kicked off by these subcommands synchronous instead of asynchronous. This functionality is implemented using a new ioctl. The type of activity to wait for is provided as input to the ioctl, and the ioctl blocks until all activity of that type has completed. An ioctl was used over other methods of kernel-userspace communiction primarily for the sake of portability. Porting Notes: This is ported from Delphix OS change DLPX-44432. The following changes were made while porting: - Added ZoL-style ioctl input declaration. - Reorganized error handling in zpool_initialize in libzfs to integrate better with changes made for TRIM support. - Fixed check for whether a checkpoint discard is in progress. Previously it also waited if the pool had a checkpoint, instead of just if a checkpoint was being discarded. - Exposed zfs_initialize_chunk_size as a ZoL-style tunable. - Updated more existing tests to make use of new 'zpool wait' functionality, tests that don't exist in Delphix OS. - Used existing ZoL tunable zfs_scan_suspend_progress, together with zinject, in place of a new tunable zfs_scan_max_blks_per_txg. - Added support for a non-integral interval argument to zpool wait. Future work: ZoL has support for trimming devices, which Delphix OS does not. In the future, 'zpool wait' could be extended to add the ability to wait for trim operations to complete. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: John Gallagher <john.gallagher@delphix.com> Closes #9162
2019-09-14 01:09:06 +00:00
.sp
.ne 2
.na
\fBzfs_initialize_chunk_size\fR (ulong)
.ad
.RS 12n
Size of writes used by \fBzpool initialize\fR.
This option is used by the test suite to facilitate testing.
.sp
Default value: \fB1,048,576\fR
.RE
Fast Clone Deletion Deleting a clone requires finding blocks are clone-only, not shared with the snapshot. This was done by traversing the entire block tree which results in a large performance penalty for sparsely written clones. This is new method keeps track of clone blocks when they are modified in a "Livelist" so that, when it’s time to delete, the clone-specific blocks are already at hand. We see performance improvements because now deletion work is proportional to the number of clone-modified blocks, not the size of the original dataset. Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Sara Hartse <sara.hartse@delphix.com> Closes #8416
2019-07-26 17:54:14 +00:00
.sp
.ne 2
.na
\fBzfs_livelist_max_entries\fR (ulong)
.ad
.RS 12n
The threshold size (in block pointers) at which we create a new sub-livelist.
Larger sublists are more costly from a memory perspective but the fewer
sublists there are, the lower the cost of insertion.
.sp
Default value: \fB500,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_min_percent_shared\fR (int)
.ad
.RS 12n
If the amount of shared space between a snapshot and its clone drops below
this threshold, the clone turns off the livelist and reverts to the old deletion
method. This is in place because once a clone has been overwritten enough
livelists no long give us a benefit.
.sp
Default value: \fB75\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_condense_new_alloc\fR (int)
.ad
.RS 12n
Incremented each time an extra ALLOC blkptr is added to a livelist entry while
it is being condensed.
This option is used by the test suite to track race conditions.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_condense_sync_cancel\fR (int)
.ad
.RS 12n
Incremented each time livelist condensing is canceled while in
spa_livelist_condense_sync.
This option is used by the test suite to track race conditions.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_condense_sync_pause\fR (int)
.ad
.RS 12n
When set, the livelist condense process pauses indefinitely before
executing the synctask - spa_livelist_condense_sync.
This option is used by the test suite to trigger race conditions.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_condense_zthr_cancel\fR (int)
.ad
.RS 12n
Incremented each time livelist condensing is canceled while in
spa_livelist_condense_cb.
This option is used by the test suite to track race conditions.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_livelist_condense_zthr_pause\fR (int)
.ad
.RS 12n
When set, the livelist condense process pauses indefinitely before
executing the open context condensing work in spa_livelist_condense_cb.
This option is used by the test suite to trigger race conditions.
.sp
Default value: \fB0\fR.
.RE
Add tunables for channel programs This patch adds tunables for modifying the maximum memory limit and maximum instruction limit that can be specified when running a channel program. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov Reviewed-by: Sara Hartse <sara.hartse@delphix.com> Signed-off-by: John Gallagher <john.gallagher@delphix.com> External-issue: LX-1085 Closes #7618
2018-06-15 22:10:42 +00:00
.sp
.ne 2
.na
\fBzfs_lua_max_instrlimit\fR (ulong)
.ad
.RS 12n
The maximum execution time limit that can be set for a ZFS channel program,
specified as a number of Lua instructions.
.sp
Default value: \fB100,000,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_lua_max_memlimit\fR (ulong)
.ad
.RS 12n
The maximum memory limit that can be set for a ZFS channel program, specified
in bytes.
.sp
Default value: \fB104,857,600\fR.
.RE
OpenZFS 9330 - stack overflow when creating a deeply nested dataset Datasets that are deeply nested (~100 levels) are impractical. We just put a limit of 50 levels to newly created datasets. Existing datasets should work without a problem. The problem can be seen by attempting to create a dataset using the -p option with many levels: panic[cpu0]/thread=ffffff01cd282c20: BAD TRAP: type=8 (#df Double fault) rp=ffffffff fffffffffbc3aa60 unix:die+100 () fffffffffbc3ab70 unix:trap+157d () ffffff00083d7020 unix:_patch_xrstorq_rbx+196 () ffffff00083d7050 zfs:dbuf_rele+2e () ... ffffff00083d7080 zfs:dsl_dir_close+32 () ffffff00083d70b0 zfs:dsl_dir_evict+30 () ffffff00083d70d0 zfs:dbuf_evict_user+4a () ffffff00083d7100 zfs:dbuf_rele_and_unlock+87 () ffffff00083d7130 zfs:dbuf_rele+2e () ... The block above repeats once per directory in the ... ... create -p command, working towards the root ... ffffff00083db9f0 zfs:dsl_dataset_drop_ref+19 () ffffff00083dba20 zfs:dsl_dataset_rele+42 () ffffff00083dba70 zfs:dmu_objset_prefetch+e4 () ffffff00083dbaa0 zfs:findfunc+23 () ffffff00083dbb80 zfs:dmu_objset_find_spa+38c () ffffff00083dbbc0 zfs:dmu_objset_find+40 () ffffff00083dbc20 zfs:zfs_ioc_snapshot_list_next+4b () ffffff00083dbcc0 zfs:zfsdev_ioctl+347 () ffffff00083dbd00 genunix:cdev_ioctl+45 () ffffff00083dbd40 specfs:spec_ioctl+5a () ffffff00083dbdc0 genunix:fop_ioctl+7b () ffffff00083dbec0 genunix:ioctl+18e () ffffff00083dbf10 unix:brand_sys_sysenter+1c9 () Porting notes: * Added zfs_max_dataset_nesting module option with documentation. * Updated zfs_rename_014_neg.ksh for Linux. * Increase the zfs.sh stack warning to 15K. Enough time has passed that 16K can be reasonably assumed to be the default value. It was increased in the 3.15 kernel released in June of 2014. Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> OpenZFS-issue: https://www.illumos.org/issues/9330 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/757a75a Closes #7681
2016-09-12 15:15:20 +00:00
.sp
.ne 2
.na
\fBzfs_max_dataset_nesting\fR (int)
.ad
.RS 12n
The maximum depth of nested datasets. This value can be tuned temporarily to
fix existing datasets that exceed the predefined limit.
.sp
Default value: \fB50\fR.
.RE
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
.sp
.ne 2
.na
\fBzfs_max_log_walking\fR (ulong)
.ad
.RS 12n
The number of past TXGs that the flushing algorithm of the log spacemap
feature uses to estimate incoming log blocks.
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_max_logsm_summary_length\fR (ulong)
.ad
.RS 12n
Maximum number of rows allowed in the summary of the spacemap log.
.sp
Default value: \fB10\fR.
.RE
Illumos 5027 - zfs large block support 5027 zfs large block support Reviewed by: Alek Pinchuk <pinchuk.alek@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5027 https://github.com/illumos/illumos-gate/commit/b515258 Porting Notes: * Included in this patch is a tiny ISP2() cleanup in zio_init() from Illumos 5255. * Unlike the upstream Illumos commit this patch does not impose an arbitrary 128K block size limit on volumes. Volumes, like filesystems, are limited by the zfs_max_recordsize=1M module option. * By default the maximum record size is limited to 1M by the module option zfs_max_recordsize. This value may be safely increased up to 16M which is the largest block size supported by the on-disk format. At the moment, 1M blocks clearly offer a significant performance improvement but the benefits of going beyond this for the majority of workloads are less clear. * The illumos version of this patch increased DMU_MAX_ACCESS to 32M. This was determined not to be large enough when using 16M blocks because the zfs_make_xattrdir() function will fail (EFBIG) when assigning a TX. This was immediately observed under Linux because all newly created files must have a security xattr created and that was failing. Therefore, we've set DMU_MAX_ACCESS to 64M. * On 32-bit platforms a hard limit of 1M is set for blocks due to the limited virtual address space. We should be able to relax this one the ABD patches are merged. Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #354
2014-11-03 20:15:08 +00:00
.sp
.ne 2
.na
\fBzfs_max_recordsize\fR (int)
.ad
.RS 12n
We currently support block sizes from 512 bytes to 16MB. The benefits of
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
larger blocks, and thus larger I/O, need to be weighed against the cost of
Illumos 5027 - zfs large block support 5027 zfs large block support Reviewed by: Alek Pinchuk <pinchuk.alek@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5027 https://github.com/illumos/illumos-gate/commit/b515258 Porting Notes: * Included in this patch is a tiny ISP2() cleanup in zio_init() from Illumos 5255. * Unlike the upstream Illumos commit this patch does not impose an arbitrary 128K block size limit on volumes. Volumes, like filesystems, are limited by the zfs_max_recordsize=1M module option. * By default the maximum record size is limited to 1M by the module option zfs_max_recordsize. This value may be safely increased up to 16M which is the largest block size supported by the on-disk format. At the moment, 1M blocks clearly offer a significant performance improvement but the benefits of going beyond this for the majority of workloads are less clear. * The illumos version of this patch increased DMU_MAX_ACCESS to 32M. This was determined not to be large enough when using 16M blocks because the zfs_make_xattrdir() function will fail (EFBIG) when assigning a TX. This was immediately observed under Linux because all newly created files must have a security xattr created and that was failing. Therefore, we've set DMU_MAX_ACCESS to 64M. * On 32-bit platforms a hard limit of 1M is set for blocks due to the limited virtual address space. We should be able to relax this one the ABD patches are merged. Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #354
2014-11-03 20:15:08 +00:00
COWing a giant block to modify one byte. Additionally, very large blocks
can have an impact on i/o latency, and also potentially on the memory
allocator. Therefore, we do not allow the recordsize to be set larger than
zfs_max_recordsize (default 1MB). Larger blocks can be created by changing
this tunable, and pools with larger blocks can always be imported and used,
regardless of this setting.
.sp
Default value: \fB1,048,576\fR.
.RE
Implement Redacted Send/Receive Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Prashanth Sreenivasa <pks@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Chris Williamson <chris.williamson@delphix.com> Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #7958
2019-06-19 16:48:13 +00:00
.sp
.ne 2
.na
\fBzfs_allow_redacted_dataset_mount\fR (int)
.ad
.RS 12n
Allow datasets received with redacted send/receive to be mounted. Normally
disabled because these datasets may be missing key data.
.sp
Default value: \fB0\fR.
.RE
Log Spacemap Project = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8442
2019-07-16 17:11:49 +00:00
.sp
.ne 2
.na
\fBzfs_min_metaslabs_to_flush\fR (ulong)
.ad
.RS 12n
Minimum number of metaslabs to flush per dirty TXG
.sp
Default value: \fB1\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
.sp
.ne 2
.na
\fBzfs_metaslab_fragmentation_threshold\fR (int)
.ad
.RS 12n
Allow metaslabs to keep their active state as long as their fragmentation
percentage is less than or equal to this value. An active metaslab that
exceeds this threshold will no longer keep its active status allowing
better metaslabs to be selected.
.sp
Default value: \fB70\fR.
.RE
.sp
.ne 2
.na
\fBzfs_mg_fragmentation_threshold\fR (int)
.ad
.RS 12n
Metaslab groups are considered eligible for allocations if their
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
fragmentation metric (measured as a percentage) is less than or equal to
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
this value. If a metaslab group exceeds this threshold then it will be
skipped unless all metaslab groups within the metaslab class have also
crossed this threshold.
.sp
Reduced IOPS when all vdevs are in the zfs_mg_fragmentation_threshold Historically while doing performance testing we've noticed that IOPS can be significantly reduced when all vdevs in the pool are hitting the zfs_mg_fragmentation_threshold percentage. Specifically in a hypothetical pool with two vdevs, what can happen is the following: Vdev A would go above that threshold and only vdev B would be used. Then vdev B would pass that threshold but vdev A would go below it (we've been freeing from A to allocate to B). The allocations would go back and forth utilizing one vdev at a time with IOPS taking a hit. Empirically, we've seen that our vdev selection for allocations is good enough that fragmentation increases uniformly across all vdevs the majority of the time. Thus we set the threshold percentage high enough to avoid hitting the speed bump on pools that are being pushed to the edge. We effectively disable its effect in the majority of the cases but we don't remove (at least for now) just in case we hit any weird behavior in the future. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8859
2019-06-06 20:08:41 +00:00
Default value: \fB95\fR.
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-19 20:19:24 +00:00
.RE
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 03:36:03 +00:00
.sp
.ne 2
.na
\fBzfs_mg_noalloc_threshold\fR (int)
.ad
.RS 12n
Defines a threshold at which metaslab groups should be eligible for
allocations. The value is expressed as a percentage of free space
beyond which a metaslab group is always eligible for allocations.
If a metaslab group's free space is less than or equal to the
Man page white space and spelling corrections Correct some misspelled words and grammatical errors, and remove trailing white space in the man pages. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4115
2015-12-17 01:45:15 +00:00
threshold, the allocator will avoid allocating to that group
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 03:36:03 +00:00
unless all groups in the pool have reached the threshold. Once all
groups have reached the threshold, all groups are allowed to accept
allocations. The default value of 0 disables the feature and causes
all metaslab groups to be eligible for allocations.
Man page fixes * ztest.1 man page: fix typo * zfs-module-parameters.5 man page: fix grammar Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> Closes #6492
2017-08-10 22:45:25 +00:00
This parameter allows one to deal with pools having heavily imbalanced
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 03:36:03 +00:00
vdevs such as would be the case when a new vdev has been added.
Setting the threshold to a non-zero percentage will stop allocations
from being made to vdevs that aren't filled to the specified percentage
and allow lesser filled vdevs to acquire more allocations than they
otherwise would under the old \fBzfs_mg_alloc_failures\fR facility.
.sp
Default value: \fB0\fR.
.RE
Pool allocation classes Allocation Classes add the ability to have allocation classes in a pool that are dedicated to serving specific block categories, such as DDT data, metadata, and small file blocks. A pool can opt-in to this feature by adding a 'special' or 'dedup' top-level VDEV. Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Alek Pinchuk <apinchuk@datto.com> Reviewed-by: Håkan Johansson <f96hajo@chalmers.se> Reviewed-by: Andreas Dilger <andreas.dilger@chamcloud.com> Reviewed-by: DHE <git@dehacked.net> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Gregor Kopka <gregor@kopka.net> Reviewed-by: Kash Pande <kash@tripleback.net> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Don Brady <don.brady@delphix.com> Closes #5182
2018-09-06 01:33:36 +00:00
.sp
.ne 2
.na
\fBzfs_ddt_data_is_special\fR (int)
.ad
.RS 12n
If enabled, ZFS will place DDT data into the special allocation class.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_user_indirect_is_special\fR (int)
.ad
.RS 12n
If enabled, ZFS will place user data (both file and zvol) indirect blocks
into the special allocation class.
.sp
Default value: \fB1\fR.
.RE
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
.ne 2
.na
\fBzfs_multihost_history\fR (int)
.ad
.RS 12n
Historical statistics for the last N multihost updates will be available in
\fB/proc/spl/kstat/zfs/<pool>/multihost\fR
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_multihost_interval\fR (ulong)
.ad
.RS 12n
Used to control the frequency of multihost writes which are performed when the
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
\fBmultihost\fR pool property is on. This is one factor used to determine the
length of the activity check during import.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
The multihost write period is \fBzfs_multihost_interval / leaf-vdevs\fR
milliseconds. On average a multihost write will be issued for each leaf vdev
every \fBzfs_multihost_interval\fR milliseconds. In practice, the observed
period can vary with the I/O load and this observed value is the delay which is
stored in the uberblock.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
Default value: \fB1000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_multihost_import_intervals\fR (uint)
.ad
.RS 12n
Used to control the duration of the activity test on import. Smaller values of
\fBzfs_multihost_import_intervals\fR will reduce the import time but increase
the risk of failing to detect an active pool. The total activity check time is
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
never allowed to drop below one second.
.sp
On import the activity check waits a minimum amount of time determined by
\fBzfs_multihost_interval * zfs_multihost_import_intervals\fR, or the same
product computed on the host which last had the pool imported (whichever is
greater). The activity check time may be further extended if the value of mmp
delay found in the best uberblock indicates actual multihost updates happened
at longer intervals than \fBzfs_multihost_interval\fR. A minimum value of
\fB100ms\fR is enforced.
.sp
A value of 0 is ignored and treated as if it was set to 1.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
Increase default zfs_multihost_fail_intervals and import_intervals By default, when multihost is enabled for a pool, the pool is suspended if (zfs_multihost_fail_intervals*zfs_multihost_interval) ms pass without a successful MMP write. This is the recommended configuration. The default value for zfs_multihost_fail_intervals has been 5, and the default value for zfs_multihost_interval has been 1000, so pool suspension occurred at 5 seconds. There have been multiple cases where a single misbehaving device in a pool triggered a SCSI reset, and all I/O paused for 5-6 seconds. This in turn caused MMP to suspend the pool. In the cases observed, the rest of the devices were healthy and the pool was otherwise correctly performing I/O. The reset was handled correctly by ZFS, and by suspending the pool MMP made replacing the device more difficult as well as forcing the host to be rebooted. Increase the default value of zfs_multihost_fail_intervals to 10, so that MMP tolerates up to 10 seconds of failed MMP writes before suspending the pool. Increase the default value of zfs_multihost_import_intervals to 20, to maintain the 2:1 safety factor. This results in a force import taking approximately 20 seconds when MMP is enabled, with default values. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7709 Closes #8495
2019-03-13 16:50:48 +00:00
Default value: \fB20\fR.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_multihost_fail_intervals\fR (uint)
.ad
.RS 12n
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
Controls the behavior of the pool when multihost write failures or delays are
detected.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
When \fBzfs_multihost_fail_intervals = 0\fR, multihost write failures or delays
are ignored. The failures will still be reported to the ZED which depending on
its configuration may take action such as suspending the pool or offlining a
device.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
MMP interval and fail_intervals in uberblock When Multihost is enabled, and a pool is imported, uberblock writes include ub_mmp_delay to allow an importing node to calculate the duration of an activity test. This value, is not enough information. If zfs_multihost_fail_intervals > 0 on the node with the pool imported, the safe minimum duration of the activity test is well defined, but does not depend on ub_mmp_delay: zfs_multihost_fail_intervals * zfs_multihost_interval and if zfs_multihost_fail_intervals == 0 on that node, there is no such well defined safe duration, but the importing host cannot tell whether mmp_delay is high due to I/O delays, or due to a very large zfs_multihost_interval setting on the host which last imported the pool. As a result, it may use a far longer period for the activity test than is necessary. This patch renames ub_mmp_sequence to ub_mmp_config and uses it to record the zfs_multihost_interval and zfs_multihost_fail_intervals values, as well as the mmp sequence. This allows a shorter activity test duration to be calculated by the importing host in most situations. These values are also added to the multihost_history kstat records. It calculates the activity test duration differently depending on whether the new fields are present or not; for importing pools with only ub_mmp_delay, it uses (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals Which results in an activity test duration less sensitive to the leaf count. In addition, it makes a few other improvements: * It updates the "sequence" part of ub_mmp_config when MMP writes in between syncs occur. This allows an importing host to detect MMP on the remote host sooner, when the pool is idle, as it is not limited to the granularity of ub_timestamp (1 second). * It issues writes immediately when zfs_multihost_interval is changed so remote hosts see the updated value as soon as possible. * It fixes a bug where setting zfs_multihost_fail_intervals = 1 results in immediate pool suspension. * Update tests to verify activity check duration is based on recorded tunable values, not tunable values on importing host. * Update tests to verify the expected number of uberblocks have valid MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number), that sequence number is incrementing, and that uberblock values match tunable settings. Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7842
2019-03-21 19:47:57 +00:00
When \fBzfs_multihost_fail_intervals > 0\fR, the pool will be suspended if
\fBzfs_multihost_fail_intervals * zfs_multihost_interval\fR milliseconds pass
without a successful mmp write. This guarantees the activity test will see
mmp writes if the pool is imported. A value of 1 is ignored and treated as
if it was set to 2. This is necessary to prevent the pool from being suspended
due to normal, small I/O latency variations.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.sp
Increase default zfs_multihost_fail_intervals and import_intervals By default, when multihost is enabled for a pool, the pool is suspended if (zfs_multihost_fail_intervals*zfs_multihost_interval) ms pass without a successful MMP write. This is the recommended configuration. The default value for zfs_multihost_fail_intervals has been 5, and the default value for zfs_multihost_interval has been 1000, so pool suspension occurred at 5 seconds. There have been multiple cases where a single misbehaving device in a pool triggered a SCSI reset, and all I/O paused for 5-6 seconds. This in turn caused MMP to suspend the pool. In the cases observed, the rest of the devices were healthy and the pool was otherwise correctly performing I/O. The reset was handled correctly by ZFS, and by suspending the pool MMP made replacing the device more difficult as well as forcing the host to be rebooted. Increase the default value of zfs_multihost_fail_intervals to 10, so that MMP tolerates up to 10 seconds of failed MMP writes before suspending the pool. Increase the default value of zfs_multihost_import_intervals to 20, to maintain the 2:1 safety factor. This results in a force import taking approximately 20 seconds when MMP is enabled, with default values. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #7709 Closes #8495
2019-03-13 16:50:48 +00:00
Default value: \fB10\fR.
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_no_scrub_io\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Set for no scrub I/O. This results in scrubs not actually scrubbing data and
simply doing a metadata crawl of the pool instead.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_no_scrub_prefetch\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Set to disable block prefetching for scrubs.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_nocacheflush\fR (int)
.ad
.RS 12n
OpenZFS 9963 - Separate tunable for disabling ZIL vdev flush Porting Notes: * Add options to zfs-module-parameters(5) man page. * zfs_nocacheflush move to vdev.c instead of vdev_disk.c, since the latter doesn't get built for user space. Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Patrick Mooney <patrick.mooney@joyent.com> Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: George Melikov <mail@gmelikov.ru> Approved by: Dan McDonald <danmcd@joyent.com> Ported-by: Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9963 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f8fdf68125 Closes #8186
2018-10-23 16:44:37 +00:00
Disable cache flush operations on disks when writing. Setting this will
cause pool corruption on power loss if a volatile out-of-order write cache
is enabled.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_nopwrite_enabled\fR (int)
.ad
.RS 12n
Enable NOP writes
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
SEEK_HOLE should not block on txg_wait_synced() Force flushing of txg's can be painfully slow when competing for disk IO, since this is a process meant to execute asynchronously. Optimize this path via allowing data/hole seeking if the file is clean, but if dirty fall back to old logic. This is a compromise to disabling the feature entirely. Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #4306 Closes #5962
2017-03-24 21:28:38 +00:00
.sp
.ne 2
.na
\fBzfs_dmu_offset_next_sync\fR (int)
.ad
.RS 12n
Enable forcing txg sync to find holes. When enabled forces ZFS to act
like prior versions when SEEK_HOLE or SEEK_DATA flags are used, which
when a dnode is dirty causes txg's to be synced so that this data can be
found.
.sp
Use \fB1\fR for yes and \fB0\fR to disable (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
Illumos 5694 - traverse_prefetcher does not prefetch enough 5694 traverse_prefetcher does not prefetch enough Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com> Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/5694 https://github.com/illumos/illumos-gate/commit/34d7ce05 Ported-by: Chris Dunlop <chris@onthe.net.au> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3230
2015-03-27 04:31:52 +00:00
\fBzfs_pd_bytes_max\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
The number of bytes which should be prefetched during a pool traversal
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 01:03:57 +00:00
(eg: \fBzfs send\fR or other data crawling operations)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update zfs_pd_bytes_max default in zfs(8) Commit b738bc5 should have updated the default value of zfs_pd_bytes_max in the zfs(8) man page. The correct default value is 50*1024*1024. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-03-31 18:51:37 +00:00
Default value: \fB52,428,800\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Add missing module_param for zfs_per_txg_dirty_frees_percent When the code was added this tunable was not exposed via module params. Also it was not documented. This patch changes the type from a uint32 to a ulong as done with other percentage tunables and also documents it in the zfs-module-parameters man page. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: David Quigley <david.quigley@intel.com> Closes #5750
2017-02-07 17:44:03 +00:00
.sp
.ne 2
.na
\fBzfs_per_txg_dirty_frees_percent \fR (ulong)
.ad
.RS 12n
Freeing throttle should account for holes Deletion throttle currently does not account for holes in a file. This means that it can activate when it shouldn't. To fix it we switch the throttle to be based on the number of L1 blocks we will have to dirty when freeing Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> Closes #7725 Closes #7888
2019-02-12 20:01:08 +00:00
Tunable to control percentage of dirtied indirect blocks from frees allowed
into one TXG. After this threshold is crossed, additional frees will wait until
the next TXG.
Add missing module_param for zfs_per_txg_dirty_frees_percent When the code was added this tunable was not exposed via module params. Also it was not documented. This patch changes the type from a uint32 to a ulong as done with other percentage tunables and also documents it in the zfs-module-parameters man page. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: David Quigley <david.quigley@intel.com> Closes #5750
2017-02-07 17:44:03 +00:00
A value of zero will disable this throttle.
.sp
Freeing throttle should account for holes Deletion throttle currently does not account for holes in a file. This means that it can activate when it shouldn't. To fix it we switch the throttle to be based on the number of L1 blocks we will have to dirty when freeing Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> Closes #7725 Closes #7888
2019-02-12 20:01:08 +00:00
Default value: \fB5\fR, set to \fB0\fR to disable.
Add missing module_param for zfs_per_txg_dirty_frees_percent When the code was added this tunable was not exposed via module params. Also it was not documented. This patch changes the type from a uint32 to a ulong as done with other percentage tunables and also documents it in the zfs-module-parameters man page. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: David Quigley <david.quigley@intel.com> Closes #5750
2017-02-07 17:44:03 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_prefetch_disable\fR (int)
.ad
.RS 12n
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-26 21:10:31 +00:00
This tunable disables predictive prefetch. Note that it leaves "prescient"
prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch,
prescient prefetch never issues i/os that end up not being needed, so it
can't hurt performance.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Code improvement and bug fixes for QAT support 1. Support QAT when ZFS is root file-system: When ZFS module is loaded before QAT started, the QAT can be started again in post-process, e.g.: echo 0 > /sys/module/zfs/parameters/zfs_qat_compress_disable echo 0 > /sys/module/zfs/parameters/zfs_qat_encrypt_disable echo 0 > /sys/module/zfs/parameters/zfs_qat_checksum_disable 2. Verify alder checksum of the de-compress result 3. Allocate Digest, IV and AAD buffer in physical contiguous memory by QAT_PHYS_CONTIG_ALLOC. 4. Update the documentation for zfs_qat_compress_disable, zfs_qat_checksum_disable, zfs_qat_encrypt_disable. Reviewed-by: Tom Caputi <tcaputi@datto.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Weigang Li <weigang.li@intel.com> Signed-off-by: Chengfeix Zhu <chengfeix.zhu@intel.com> Closes #8323 Closes #8610
2019-04-16 19:38:36 +00:00
.sp
.ne 2
.na
\fBzfs_qat_checksum_disable\fR (int)
.ad
.RS 12n
This tunable disables qat hardware acceleration for sha256 checksums. It
may be set after the zfs modules have been loaded to initialize the qat
hardware as long as support is compiled in and the qat driver is present.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_qat_compress_disable\fR (int)
.ad
.RS 12n
This tunable disables qat hardware acceleration for gzip compression. It
may be set after the zfs modules have been loaded to initialize the qat
hardware as long as support is compiled in and the qat driver is present.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_qat_encrypt_disable\fR (int)
.ad
.RS 12n
This tunable disables qat hardware acceleration for AES-GCM encryption. It
may be set after the zfs modules have been loaded to initialize the qat
hardware as long as support is compiled in and the qat driver is present.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_read_chunk_size\fR (long)
.ad
.RS 12n
Bytes to read per chunk
.sp
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_read_history\fR (int)
.ad
.RS 12n
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
Historical statistics for the last N reads will be available in
\fB/proc/spl/kstat/zfs/<pool>/reads\fR
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB0\fR (no data is kept).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_read_history_hits\fR (int)
.ad
.RS 12n
Include cache hits in read history
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Add device rebuild feature The device_rebuild feature enables sequential reconstruction when resilvering. Mirror vdevs can be rebuilt in LBA order which may more quickly restore redundancy depending on the pools average block size, overall fragmentation and the performance characteristics of the devices. However, block checksums cannot be verified as part of the rebuild thus a scrub is automatically started after the sequential resilver completes. The new '-s' option has been added to the `zpool attach` and `zpool replace` command to request sequential reconstruction instead of healing reconstruction when resilvering. zpool attach -s <pool> <existing vdev> <new vdev> zpool replace -s <pool> <old vdev> <new vdev> The `zpool status` output has been updated to report the progress of sequential resilvering in the same way as healing resilvering. The one notable difference is that multiple sequential resilvers may be in progress as long as they're operating on different top-level vdevs. The `zpool wait -t resilver` command was extended to wait on sequential resilvers. From this perspective they are no different than healing resilvers. Sequential resilvers cannot be supported for RAIDZ, but are compatible with the dRAID feature being developed. As part of this change the resilver_restart_* tests were moved in to the functional/replacement directory. Additionally, the replacement tests were renamed and extended to verify both resilvering and rebuilding. Original-patch-by: Isaac Huang <he.huang@intel.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: John Poduska <jpoduska@datto.com> Co-authored-by: Mark Maybee <mmaybee@cray.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #10349
2020-07-03 18:05:50 +00:00
.sp
.ne 2
.na
\fBzfs_rebuild_max_segment\fR (ulong)
.ad
.RS 12n
Maximum read segment size to issue when sequentially resilvering a
top-level vdev.
.sp
Default value: \fB1,048,576\fR.
.RE
Distributed Spare (dRAID) Feature This patch adds a new top-level vdev type called dRAID, which stands for Distributed parity RAID. This pool configuration allows all dRAID vdevs to participate when rebuilding to a distributed hot spare device. This can substantially reduce the total time required to restore full parity to pool with a failed device. A dRAID pool can be created using the new top-level `draid` type. Like `raidz`, the desired redundancy is specified after the type: `draid[1,2,3]`. No additional information is required to create the pool and reasonable default values will be chosen based on the number of child vdevs in the dRAID vdev. zpool create <pool> draid[1,2,3] <vdevs...> Unlike raidz, additional optional dRAID configuration values can be provided as part of the draid type as colon separated values. This allows administrators to fully specify a layout for either performance or capacity reasons. The supported options include: zpool create <pool> \ draid[<parity>][:<data>d][:<children>c][:<spares>s] \ <vdevs...> - draid[parity] - Parity level (default 1) - draid[:<data>d] - Data devices per group (default 8) - draid[:<children>c] - Expected number of child vdevs - draid[:<spares>s] - Distributed hot spares (default 0) Abbreviated example `zpool status` output for a 68 disk dRAID pool with two distributed spares using special allocation classes. ``` pool: tank state: ONLINE config: NAME STATE READ WRITE CKSUM slag7 ONLINE 0 0 0 draid2:8d:68c:2s-0 ONLINE 0 0 0 L0 ONLINE 0 0 0 L1 ONLINE 0 0 0 ... U25 ONLINE 0 0 0 U26 ONLINE 0 0 0 spare-53 ONLINE 0 0 0 U27 ONLINE 0 0 0 draid2-0-0 ONLINE 0 0 0 U28 ONLINE 0 0 0 U29 ONLINE 0 0 0 ... U42 ONLINE 0 0 0 U43 ONLINE 0 0 0 special mirror-1 ONLINE 0 0 0 L5 ONLINE 0 0 0 U5 ONLINE 0 0 0 mirror-2 ONLINE 0 0 0 L6 ONLINE 0 0 0 U6 ONLINE 0 0 0 spares draid2-0-0 INUSE currently in use draid2-0-1 AVAIL ``` When adding test coverage for the new dRAID vdev type the following options were added to the ztest command. These options are leverages by zloop.sh to test a wide range of dRAID configurations. -K draid|raidz|random - kind of RAID to test -D <value> - dRAID data drives per group -S <value> - dRAID distributed hot spares -R <value> - RAID parity (raidz or dRAID) The zpool_create, zpool_import, redundancy, replacement and fault test groups have all been updated provide test coverage for the dRAID feature. Co-authored-by: Isaac Huang <he.huang@intel.com> Co-authored-by: Mark Maybee <mmaybee@cray.com> Co-authored-by: Don Brady <don.brady@delphix.com> Co-authored-by: Matthew Ahrens <mahrens@delphix.com> Co-authored-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Mark Maybee <mmaybee@cray.com> Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #10102
2020-11-13 21:51:51 +00:00
.sp
.ne 2
.na
\fBzfs_rebuild_scrub_enabled\fR (int)
.ad
.RS 12n
Automatically start a pool scrub when the last active sequential resilver
completes in order to verify the checksums of all blocks which have been
resilvered. This option is enabled by default and is strongly recommended.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_rebuild_vdev_limit\fR (ulong)
.ad
.RS 12n
Maximum amount of i/o that can be concurrently issued for a sequential
resilver per leaf device, given in bytes.
.sp
Default value: \fB33,554,432\fR.
.RE
OpenZFS 9290 - device removal reduces redundancy of mirrors Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy. Note that in no case is incorrect data returned, but we might get a checksum error when we should have been able to find the right data. There are two underlying problems: 1. When we remove a mirror device, we only read one side of the mirror. Since we can't verify the checksum, this side may be silently bad, but the good data is on the other side of the mirror (which we didn't read). This can cause the removal to "bake in" the busted data – all copies of the data in the new location are the same, busted version, while we left the good version behind. The fix for this is to read and copy both sides of the mirror. If the old and new vdevs are mirrors, we will read both sides of the old mirror, and write each copy to the corresponding side of the new mirror. (If the old and new vdevs have a different number of children, we will do this as best as possible.) Even though we aren't verifying checksums, this ensures that as long as there's a good copy of the data, we'll have a good copy after the removal, even if there's silent damage to one side of the mirror. If we're removing a mirror that has some silent damage, we'll have exactly the same damage in the new location (assuming that the new location is also a mirror). 2. When we read from an indirect vdev that points to a mirror vdev, we only consider one copy of the data. This can lead to reduced effective redundancy, because we might read a bad copy of the data from one side of the mirror, and not retry the other, good side of the mirror. Note that the problem is not with the removal process, but rather after the removal has completed (having copied correct data to both sides of the mirror), if one side of the new mirror is silently damaged, we encounter the problem when reading the relocated data via the indirect vdev. Also note that the problem doesn't occur when ZFS knows that one side of the mirror is bad, e.g. when a disk entirely fails or is offlined. The impact is that reads (from indirect vdevs that point to mirrors) may return a checksum error even though the good data exists on one side of the mirror, and scrub doesn't repair all data on the mirror (if some of it is pointed to via an indirect vdev). The fix for this is complicated by "split blocks" - one logical block may be split into two (or more) pieces with each piece moved to a different new location. In this case we need to read all versions of each split (one from each side of the mirror), and figure out which combination of versions results in the correct checksum, and then repair the incorrect versions. This ensures that we supply the same redundancy whether you use device removal or not. For example, if a mirror has small silent errors on all of its children, we can still reconstruct the correct data, as long as those errors are at sufficiently-separated offsets (specifically, separated by the largest block size - default of 128KB, but up to 16MB). Porting notes: * A new indirect vdev check was moved from dsl_scan_needs_resilver_cb() to dsl_scan_needs_resilver(), which was added to ZoL as part of the sequential scrub work. * Passed NULL for zfs_ereport_post_checksum()'s zbookmark_phys_t parameter. The extra parameter is unique to ZoL. * When posting indirect checksum errors the ABD can be passed directly, zfs_ereport_post_checksum() is not yet ABD-aware in OpenZFS. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9290 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/591 Closes #6900
2018-02-13 19:37:56 +00:00
.sp
.ne 2
.na
Optimize possible split block search space Remove duplicate segment copies to minimize the possible search space for reconstruction. Once reduced an accurate assessment can be made regarding the difficulty in reconstructing the block. Also, ztest will now run zdb with zfs_reconstruct_indirect_combinations_max set to 1000000 in an attempt to avoid checksum errors. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6900
2018-03-29 21:50:40 +00:00
\fBzfs_reconstruct_indirect_combinations_max\fR (int)
.ad
.RS 12na
If an indirect split block contains more than this many possible unique
combinations when being reconstructed, consider it too computationally
expensive to check them all. Instead, try at most
\fBzfs_reconstruct_indirect_combinations_max\fR randomly-selected
combinations each time the block is accessed. This allows all segment
copies to participate fairly in the reconstruction when all combinations
cannot be checked and prevents repeated use of one bad copy.
.sp
ztest: split block reconstruction Increase the default allowed number of reconstruction attempts. There's not an exact right number for this setting. It needs to be set large enough to cover any realistic failure scenarios and small enough to avoid stalling the IO pipeline and invoking the dead man detection. The current value of 256 was empirically determined to be too low based on multi-day runs of ztest. The fault injection code would inject more damage than could be reconstructed given the relatively small number of attempts. However, in all observed cases the block could be reconstructed using a slightly higher limit. Based on local testing increasing the default value to 4096 was determined to strike the best balance. Checking all combinations takes less than 10s in the worst case, and has so far eliminated the vast majority of false positives detected by ztest. This delay is roughly on par with how long retries may be performed to a misbehaving HDD and was deemed to be reasonable. Better to err on the side of a brief delay rather than fail to reconstruct the data. Lastly, the -Y flag has been added to zdb to make it easy to try all possible combinations when performing split block reconstruction. For badly damaged blocks with 18 splits, they can be fully enumerated within a few minutes. This has been done to ensure permanent errors are never incorrectly reported when ztest verifies the pool with zdb. Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8271
2019-01-16 22:10:02 +00:00
Default value: \fB4096\fR.
OpenZFS 9290 - device removal reduces redundancy of mirrors Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy. Note that in no case is incorrect data returned, but we might get a checksum error when we should have been able to find the right data. There are two underlying problems: 1. When we remove a mirror device, we only read one side of the mirror. Since we can't verify the checksum, this side may be silently bad, but the good data is on the other side of the mirror (which we didn't read). This can cause the removal to "bake in" the busted data – all copies of the data in the new location are the same, busted version, while we left the good version behind. The fix for this is to read and copy both sides of the mirror. If the old and new vdevs are mirrors, we will read both sides of the old mirror, and write each copy to the corresponding side of the new mirror. (If the old and new vdevs have a different number of children, we will do this as best as possible.) Even though we aren't verifying checksums, this ensures that as long as there's a good copy of the data, we'll have a good copy after the removal, even if there's silent damage to one side of the mirror. If we're removing a mirror that has some silent damage, we'll have exactly the same damage in the new location (assuming that the new location is also a mirror). 2. When we read from an indirect vdev that points to a mirror vdev, we only consider one copy of the data. This can lead to reduced effective redundancy, because we might read a bad copy of the data from one side of the mirror, and not retry the other, good side of the mirror. Note that the problem is not with the removal process, but rather after the removal has completed (having copied correct data to both sides of the mirror), if one side of the new mirror is silently damaged, we encounter the problem when reading the relocated data via the indirect vdev. Also note that the problem doesn't occur when ZFS knows that one side of the mirror is bad, e.g. when a disk entirely fails or is offlined. The impact is that reads (from indirect vdevs that point to mirrors) may return a checksum error even though the good data exists on one side of the mirror, and scrub doesn't repair all data on the mirror (if some of it is pointed to via an indirect vdev). The fix for this is complicated by "split blocks" - one logical block may be split into two (or more) pieces with each piece moved to a different new location. In this case we need to read all versions of each split (one from each side of the mirror), and figure out which combination of versions results in the correct checksum, and then repair the incorrect versions. This ensures that we supply the same redundancy whether you use device removal or not. For example, if a mirror has small silent errors on all of its children, we can still reconstruct the correct data, as long as those errors are at sufficiently-separated offsets (specifically, separated by the largest block size - default of 128KB, but up to 16MB). Porting notes: * A new indirect vdev check was moved from dsl_scan_needs_resilver_cb() to dsl_scan_needs_resilver(), which was added to ZoL as part of the sequential scrub work. * Passed NULL for zfs_ereport_post_checksum()'s zbookmark_phys_t parameter. The extra parameter is unique to ZoL. * When posting indirect checksum errors the ABD can be passed directly, zfs_ereport_post_checksum() is not yet ABD-aware in OpenZFS. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9290 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/591 Closes #6900
2018-02-13 19:37:56 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_recover\fR (int)
.ad
.RS 12n
Set to attempt to recover from fatal errors. This should only be used as a
last resort, as it typically results in leaked space, or worse.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Detect IO errors during device removal * Detect IO errors during device removal While device removal cannot verify the checksums of individual blocks during device removal, it can reasonably detect hard IO errors from the leaf vdevs. Failure to perform this error checking can result in device removal completing successfully, but moving no data which will permanently corrupt the pool. Situation 1: faulted/degraded vdevs In the configuration shown below, the removal of mirror-0 will permanently corrupt the pool. Device removal will preferentially copy data from 'vdev1 -> vdev3' and from 'vdev2 -> vdev4'. Which in this case will result in nothing being copied since one vdev in each of those groups in unavailable. However, device removal will complete successfully since all IO errors are ignored. tank DEGRADED 0 0 0 mirror-0 DEGRADED 0 0 0 /var/tmp/vdev1 FAULTED 0 0 0 external fault /var/tmp/vdev2 ONLINE 0 0 0 mirror-1 DEGRADED 0 0 0 /var/tmp/vdev3 ONLINE 0 0 0 /var/tmp/vdev4 FAULTED 0 0 0 external fault This issue is resolved by updating the source child selection logic to exclude unreadable leaf vdevs. Additionally, unwritable destination child vdevs which can never succeed are skipped to prevent generating a large number of write IO errors. Situation 2: individual hard IO errors During removal if an unexpected hard IO error is encountered when either reading or writing the child vdev the entire removal operation is cancelled. While it may be possible to reconstruct the data after removal that cannot be guaranteed. The only strictly safe thing to do is to cancel the removal. As a future improvement we may want to instead suspend the removal process and allow the damaged region to be retried. But that work is left for another time, hard IO errors during the removal process are expected to be exceptionally rare. Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #6900 Closes #8161
2018-12-04 17:37:37 +00:00
.sp
.ne 2
.na
\fBzfs_removal_ignore_errors\fR (int)
.ad
.RS 12n
.sp
Ignore hard IO errors during device removal. When set, if a device encounters
a hard IO error during the removal process the removal will not be cancelled.
This can result in a normally recoverable block becoming permanently damaged
and is not recommended. This should only be used as a last resort when the
pool cannot be returned to a healthy state prior to removing the device.
.sp
Default value: \fB0\fR.
.RE
panic in removal_remap test on 4K devices If the zfs_remove_max_segment tunable is changed to be not a multiple of the sector size, then the device removal code will malfunction and try to create mappings that are smaller than one sector, leading to a panic. On debug bits this assertion will fail in spa_vdev_copy_segment(): ASSERT3U(DVA_GET_ASIZE(&dst), ==, size); On nondebug, the system panics with a stack like: metaslab_free_concrete() metaslab_free_impl() metaslab_free_impl_cb() vdev_indirect_remap() free_from_removing_vdev() metaslab_free_impl() metaslab_free_dva() metaslab_free() Fortunately, the default for zfs_remove_max_segment is 1MB, so this can't occur by default. We hit it during this test because removal_remap.ksh changes zfs_remove_max_segment to 1KB. When testing on 4KB-sector disks, we hit the bug. This change makes the zfs_remove_max_segment tunable more robust, automatically rounding it up to a multiple of the sector size. We also turn some key assertions into VERIFY's so that similar bugs would be caught before they are encoded on disk (and thus avoid a panic-reboot-loop). Reviewed-by: Sean Eric Fagan <sef@ixsystems.com> Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-61342 Closes #8893
2019-06-13 20:12:39 +00:00
.sp
.ne 2
.na
\fBzfs_removal_suspend_progress\fR (int)
.ad
.RS 12n
.sp
This is used by the test suite so that it can ensure that certain actions
happen while in the middle of a removal.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_remove_max_segment\fR (int)
.ad
.RS 12n
.sp
The largest contiguous segment that we will attempt to allocate when removing
a device. This can be no larger than 16MB. If there is a performance
problem with attempting to allocate large blocks, consider decreasing this.
.sp
Default value: \fB16,777,216\fR (16MB).
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_resilver_disable_defer\fR (int)
.ad
.RS 12n
Disables the \fBresilver_defer\fR feature, causing an operation that would
start a resilver to restart one in progress immediately.
.sp
Default value: \fB0\fR (feature enabled).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_resilver_min_time_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Resilvers are processed by the sync thread. While resilvering it will spend
at least this much time working on a resilver between txg flushes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Default value: \fB3,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Add zfs_scan_ignore_errors tunable When it's set, a DTL range will be cleared even if its scan/scrub had errors. This allows to work around resilver/scrub upon import when the pool has errors. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #7293
2018-03-13 17:43:14 +00:00
.sp
.ne 2
.na
\fBzfs_scan_ignore_errors\fR (int)
.ad
.RS 12n
If set to a nonzero value, remove the DTL (dirty time list) upon
completion of a pool scan (scrub) even if there were unrepairable
errors. It is intended to be used during pool repair or recovery to
stop resilvering when the pool is next imported.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_scrub_min_time_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Scrubs are processed by the sync thread. While scrubbing it will spend
at least this much time working on a scrub between txg flushes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Default value: \fB1,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_scan_checkpoint_intval\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
To preserve progress across reboots the sequential scan algorithm periodically
needs to stop metadata scanning and issue all the verifications I/Os to disk.
The frequency of this flushing is determined by the
Fix duplicate "fB" typo Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <guss80@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: bunder2015 <omfgbunder@gmail.com> Signed-off-by: ajs124 <git@ajs124.de> Closes #7649
2018-06-25 16:50:01 +00:00
\fBzfs_scan_checkpoint_intval\fR tunable.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Default value: \fB7200\fR seconds (every 2 hours).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_scan_fill_weight\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
This tunable affects how scrub and resilver I/O segments are ordered. A higher
number indicates that we care more about how filled in a segment is, while a
lower number indicates we care more about the size of the extent without
considering the gaps within a segment. This value is only tunable upon module
insertion. Changing the value afterwards will have no affect on scrub or
resilver performance.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Default value: \fB3\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
\fBzfs_scan_issue_strategy\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Determines the order that data will be verified while scrubbing or resilvering.
If set to \fB1\fR, data will be verified as sequentially as possible, given the
amount of memory reserved for scrubbing (see \fBzfs_scan_mem_lim_fact\fR). This
may improve scrub performance if the pool's data is very fragmented. If set to
\fB2\fR, the largest mostly-contiguous chunk of found data will be verified
first. By deferring scrubbing of small segments, we may later find adjacent data
to coalesce and increase the segment size. If set to \fB0\fR, zfs will use
strategy \fB1\fR during normal verification and strategy \fB2\fR while taking a
checkpoint.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_legacy\fR (int)
.ad
.RS 12n
A value of 0 indicates that scrubs and resilvers will gather metadata in
memory before issuing sequential I/O. A value of 1 indicates that the legacy
algorithm will be used where I/O is initiated as soon as it is discovered.
Changing this value to 0 will not affect scrubs or resilvers that are already
in progress.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_max_ext_gap\fR (int)
.ad
.RS 12n
Indicates the largest gap in bytes between scrub / resilver I/Os that will still
be considered sequential for sorting purposes. Changing this value will not
affect scrubs or resilvers that are already in progress.
.sp
Default value: \fB2097152 (2 MB)\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_mem_lim_fact\fR (int)
.ad
.RS 12n
Maximum fraction of RAM used for I/O sorting by sequential scan algorithm.
This tunable determines the hard limit for I/O sorting memory usage.
When the hard limit is reached we stop scanning metadata and start issuing
data verification I/O. This is done until we get below the soft limit.
.sp
Default value: \fB20\fR which is 5% of RAM (1/20).
.RE
.sp
.ne 2
.na
\fBzfs_scan_mem_lim_soft_fact\fR (int)
.ad
.RS 12n
The fraction of the hard limit used to determined the soft limit for I/O sorting
Fix typos in man/ Reviewed-by: Ryan Moeller <ryan@ixsystems.com> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Closes #9233
2019-08-30 16:41:35 +00:00
by the sequential scan algorithm. When we cross this limit from below no action
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
is taken. When we cross this limit from above it is because we are issuing
verification I/O. In this case (unless the metadata scan is done) we stop
issuing verification I/O and start scanning metadata again until we get to the
hard limit.
.sp
Default value: \fB20\fR which is 5% of the hard limit (1/20).
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_scan_strict_mem_lim\fR (int)
.ad
.RS 12n
Enforces tight memory limits on pool scans when a sequential scan is in
progress. When disabled the memory limit may be exceeded by fast disks.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_suspend_progress\fR (int)
.ad
.RS 12n
Freezes a scrub/resilver in progress without actually pausing it. Intended for
testing/debugging.
.sp
Default value: \fB0\fR.
.RE
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 01:27:01 +00:00
.sp
.ne 2
.na
\fBzfs_scan_vdev_limit\fR (int)
.ad
.RS 12n
Maximum amount of data that can be concurrently issued at once for scrubs and
resilvers per leaf device, given in bytes.
.sp
Default value: \fB41943040\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Add zfs_send_corrupt_data module option Tuning setting to ignore read/checksum errors when sending data. Signed-off-by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1982 Issue #1897
2013-12-17 21:53:52 +00:00
.sp
.ne 2
.na
\fBzfs_send_corrupt_data\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Allow sending of corrupt data (ignore read/checksum errors when sending data)
Add zfs_send_corrupt_data module option Tuning setting to ignore read/checksum errors when sending data. Signed-off-by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1982 Issue #1897
2013-12-17 21:53:52 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Fix send/recv lost spill block When receiving a DRR_OBJECT record the receive_object() function needs to determine how to handle a spill block associated with the object. It may need to be removed or kept depending on how the object was modified at the source. This determination is currently accomplished using a heuristic which takes in to account the DRR_OBJECT record and the existing object properties. This is a problem because there isn't quite enough information available to do the right thing under all circumstances. For example, when only the block size changes the spill block is removed when it should be kept. What's needed to resolve this is an additional flag in the DRR_OBJECT which indicates if the object being received references a spill block. The DRR_OBJECT_SPILL flag was added for this purpose. When set then the object references a spill block and it must be kept. Either it is update to date, or it will be replaced by a subsequent DRR_SPILL record. Conversely, if the object being received doesn't reference a spill block then any existing spill block should always be removed. Since previous versions of ZFS do not understand this new flag additional DRR_SPILL records will be inserted in to the stream. This has the advantage of being fully backward compatible. Existing ZFS systems receiving this stream will recreate the spill block if it was incorrectly removed. Updated ZFS versions will correctly ignore the additional spill blocks which can be identified by checking for the DRR_SPILL_UNMODIFIED flag. The small downside to this approach is that is may increase the size of the stream and of the received snapshot on previous versions of ZFS. Additionally, when receiving streams generated by previous unpatched versions of ZFS spill blocks may still be lost. OpenZFS-issue: https://www.illumos.org/issues/9952 FreeBSD-issue: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233277 Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8668
2019-05-07 22:18:44 +00:00
.sp
.ne 2
.na
\fBzfs_send_unmodified_spill_blocks\fR (int)
.ad
.RS 12n
Include unmodified spill blocks in the send stream. Under certain circumstances
previous versions of ZFS could incorrectly remove the spill block from an
existing object. Including unmodified copies of the spill blocks creates a
backwards compatible stream which will recreate a spill block if it was
incorrectly removed.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
Implement Redacted Send/Receive Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Prashanth Sreenivasa <pks@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Chris Williamson <chris.williamson@delphix.com> Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #7958
2019-06-19 16:48:13 +00:00
.sp
.ne 2
.na
\fBzfs_send_no_prefetch_queue_ff\fR (int)
.ad
.RS 12n
The fill fraction of the \fBzfs send\fR internal queues. The fill fraction
controls the timing with which internal threads are woken up.
.sp
Default value: \fB20\fR.
.RE
.sp
.ne 2
.na
\fBzfs_send_no_prefetch_queue_length\fR (int)
.ad
.RS 12n
The maximum number of bytes allowed in \fBzfs send\fR's internal queues.
.sp
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_send_queue_ff\fR (int)
.ad
.RS 12n
The fill fraction of the \fBzfs send\fR prefetch queue. The fill fraction
controls the timing with which internal threads are woken up.
.sp
Default value: \fB20\fR.
.RE
Fix 'zfs send/recv' hang with 16M blocks When using 16MB blocks the send/recv queue's aren't quite big enough. This change leaves the default 16M queue size which a good value for most pools. But it additionally ensures that the queue sizes are at least twice the allowed zfs_max_recordsize. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7365 Closes #7404
2018-04-09 02:41:15 +00:00
.sp
.ne 2
.na
\fBzfs_send_queue_length\fR (int)
.ad
.RS 12n
Implement Redacted Send/Receive Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Prashanth Sreenivasa <pks@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Chris Williamson <chris.williamson@delphix.com> Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #7958
2019-06-19 16:48:13 +00:00
The maximum number of bytes allowed that will be prefetched by \fBzfs send\fR.
This value must be at least twice the maximum block size in use.
Fix 'zfs send/recv' hang with 16M blocks When using 16MB blocks the send/recv queue's aren't quite big enough. This change leaves the default 16M queue size which a good value for most pools. But it additionally ensures that the queue sizes are at least twice the allowed zfs_max_recordsize. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7365 Closes #7404
2018-04-09 02:41:15 +00:00
.sp
Default value: \fB16,777,216\fR.
.RE
Implement Redacted Send/Receive Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Prashanth Sreenivasa <pks@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Chris Williamson <chris.williamson@delphix.com> Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #7958
2019-06-19 16:48:13 +00:00
.sp
.ne 2
.na
\fBzfs_recv_queue_ff\fR (int)
.ad
.RS 12n
The fill fraction of the \fBzfs receive\fR queue. The fill fraction
controls the timing with which internal threads are woken up.
.sp
Default value: \fB20\fR.
.RE
Fix 'zfs send/recv' hang with 16M blocks When using 16MB blocks the send/recv queue's aren't quite big enough. This change leaves the default 16M queue size which a good value for most pools. But it additionally ensures that the queue sizes are at least twice the allowed zfs_max_recordsize. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7365 Closes #7404
2018-04-09 02:41:15 +00:00
.sp
.ne 2
.na
\fBzfs_recv_queue_length\fR (int)
.ad
.RS 12n
The maximum number of bytes allowed in the \fBzfs receive\fR queue. This value
must be at least twice the maximum block size in use.
.sp
Default value: \fB16,777,216\fR.
.RE
Improve zfs receive performance by batching writes For each WRITE record in the stream, `zfs receive` creates a DMU transaction (`dmu_tx_create()`) and writes this block's data into the object. If per-block overheads (as opposed to per-byte overheads) dominate performance (as is often the case with small recordsize), the per-dmu-transaction overheads can be significant. For example, in some workloads the `receieve_writer` thread is 100% on CPU, and more than half of its CPU time is in these per-tx routines (e.g. dmu_tx_hold_write, dmu_tx_assign, dmu_tx_commit). To improve performance of `zfs receive`, this commit batches WRITE records which are to nearby offsets of the same object, and uses one DMU transaction to write them all. By default the batch size is 1MB, which for recordsize=8K reduces the number of DMU transactions by 128x for full send streams (incrementals will depend on how "clumpy" the changed blocks are). This commit improves the performance of `dd if=stream | zfs recv` from 78,800 blocks/sec to 98,100 blocks/sec (25% improvement). Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10099
2020-03-16 18:51:56 +00:00
.sp
.ne 2
.na
\fBzfs_recv_write_batch_size\fR (int)
.ad
.RS 12n
The maximum amount of data (in bytes) that \fBzfs receive\fR will write in
one DMU transaction. This is the uncompressed size, even when receiving a
compressed send stream. This setting will not reduce the write size below
a single block. Capped at a maximum of 32MB
.sp
Default value: \fB1MB\fR.
.RE
Implement Redacted Send/Receive Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Prashanth Sreenivasa <pks@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Chris Williamson <chris.williamson@delphix.com> Reviewed-by: Pavel Zhakarov <pavel.zakharov@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #7958
2019-06-19 16:48:13 +00:00
.sp
.ne 2
.na
\fBzfs_override_estimate_recordsize\fR (ulong)
.ad
.RS 12n
Setting this variable overrides the default logic for estimating block
sizes when doing a zfs send. The default heuristic is that the average
block size will be the current recordsize. Override this value if most data
in your dataset is not of that size and you require accurate zfs send size
estimates.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_sync_pass_deferred_free\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Flushing of data to disk is done in passes. Defer frees starting in this pass
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB2\fR.
.RE
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-16 22:11:29 +00:00
.sp
.ne 2
.na
\fBzfs_spa_discard_memory_limit\fR (int)
.ad
.RS 12n
Maximum memory used for prefetching a checkpoint's space map on each
vdev while discarding the checkpoint.
.sp
Default value: \fB16,777,216\fR.
.RE
Make zfs_special_class_metadata_reserve_pct into a parameter Exported and documented a new module parameter. Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #8706
2019-05-07 22:34:42 +00:00
.sp
.ne 2
.na
\fBzfs_special_class_metadata_reserve_pct\fR (int)
.ad
.RS 12n
Only allow small data blocks to be allocated on the special and dedup vdev
types when the available free space percentage on these vdevs exceeds this
value. This ensures reserved space is available for pool meta data as the
special vdevs approach capacity.
.sp
Default value: \fB25\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_sync_pass_dont_compress\fR (int)
.ad
.RS 12n
man: Canonicalize .TH usage * Use all caps for document title. * Remove section name as it can be inferred from the section number. * Name "OpenZFS" as the document source. * Bump modification date. While here, fixed trailing whitespace reported by igor. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #10792
2020-08-25 04:25:28 +00:00
Starting in this sync pass, we disable compression (including of metadata).
compress metadata in later sync passes Starting in sync pass 5 (zfs_sync_pass_dont_compress), we disable compression (including of metadata). Ostensibly this helps the sync passes to converge (i.e. for a sync pass to not need to allocate anything because it is 100% overwrites). However, in practice it increases the average number of sync passes, because when we turn compression off, a lot of block's size will change and thus we have to re-allocate (not overwrite) them. It also increases the number of 128KB allocations (e.g. for indirect blocks and spacemaps) because these will not be compressed. The 128K allocations are especially detrimental to performance on highly fragmented systems, which may have very few free segments of this size, and may need to load new metaslabs to satisfy 128K allocations. We should increase zfs_sync_pass_dont_compress. In practice on a highly fragmented system we see a few 5-pass txg's, a tiny number of 6-pass txg's, and no txg's with more than 6 passes. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-63431 Closes #8892
2019-06-13 20:10:19 +00:00
With the default setting, in practice, we don't have this many sync passes,
so this has no effect.
.sp
The original intent was that disabling compression would help the sync passes
to converge. However, in practice disabling compression increases the average
number of sync passes, because when we turn compression off, a lot of block's
size will change and thus we have to re-allocate (not overwrite) them. It
also increases the number of 128KB allocations (e.g. for indirect blocks and
spacemaps) because these will not be compressed. The 128K allocations are
especially detrimental to performance on highly fragmented systems, which may
have very few free segments of this size, and may need to load new metaslabs
to satisfy 128K allocations.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
compress metadata in later sync passes Starting in sync pass 5 (zfs_sync_pass_dont_compress), we disable compression (including of metadata). Ostensibly this helps the sync passes to converge (i.e. for a sync pass to not need to allocate anything because it is 100% overwrites). However, in practice it increases the average number of sync passes, because when we turn compression off, a lot of block's size will change and thus we have to re-allocate (not overwrite) them. It also increases the number of 128KB allocations (e.g. for indirect blocks and spacemaps) because these will not be compressed. The 128K allocations are especially detrimental to performance on highly fragmented systems, which may have very few free segments of this size, and may need to load new metaslabs to satisfy 128K allocations. We should increase zfs_sync_pass_dont_compress. In practice on a highly fragmented system we see a few 5-pass txg's, a tiny number of 6-pass txg's, and no txg's with more than 6 passes. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-63431 Closes #8892
2019-06-13 20:10:19 +00:00
Default value: \fB8\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_sync_pass_rewrite\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Rewrite new block pointers starting in this pass
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB2\fR.
.RE
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.sp
.ne 2
.na
\fBzfs_sync_taskq_batch_pct\fR (int)
.ad
.RS 12n
This controls the number of threads used by the dp_sync_taskq. The default
value of 75% will create a maximum of one thread per cpu.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB75\fR%.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.RE
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_trim_extent_bytes_max\fR (uint)
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.ad
.RS 12n
Maximum size of TRIM command. Ranges larger than this will be split in to
chunks no larger than \fBzfs_trim_extent_bytes_max\fR bytes before being
issued to the device.
.sp
Default value: \fB134,217,728\fR.
.RE
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_trim_extent_bytes_min\fR (uint)
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.ad
.RS 12n
Minimum size of TRIM commands. TRIM ranges smaller than this will be skipped
unless they're part of a larger range which was broken in to chunks. This is
done because it's common for these small TRIMs to negatively impact overall
performance. This value can be set to 0 to TRIM all unallocated space.
.sp
Default value: \fB32,768\fR.
.RE
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_trim_metaslab_skip\fR (uint)
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.ad
.RS 12n
Skip uninitialized metaslabs during the TRIM process. This option is useful
for pools constructed from large thinly-provisioned devices where TRIM
operations are slow. As a pool ages an increasing fraction of the pools
metaslabs will be initialized progressively degrading the usefulness of
this option. This setting is stored when starting a manual TRIM and will
persist for the duration of the requested TRIM.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_trim_queue_limit\fR (uint)
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.ad
.RS 12n
Maximum number of queued TRIMs outstanding per leaf vdev. The number of
concurrent TRIM commands issued to the device is controlled by the
\fBzfs_vdev_trim_min_active\fR and \fBzfs_vdev_trim_max_active\fR module
options.
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
\fBzfs_trim_txg_batch\fR (uint)
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.ad
.RS 12n
The number of transaction groups worth of frees which should be aggregated
before TRIM operations are issued to the device. This setting represents a
trade-off between issuing larger, more efficient TRIM operations and the
delay before the recently trimmed space is available for use by the device.
.sp
Increasing this value will allow frees to be aggregated for a longer time.
This will result is larger TRIM operations and potentially increased memory
usage. Decreasing this value will have the opposite effect. The default
value of 32 was determined to be a reasonable compromise.
.sp
Default value: \fB32\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_txg_history\fR (int)
.ad
.RS 12n
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 03:20:35 +00:00
Historical statistics for the last N txgs will be available in
\fB/proc/spl/kstat/zfs/<pool>/txgs\fR
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_txg_timeout\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Flush dirty data to disk at least every N seconds (maximum txg duration)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB5\fR.
.RE
Add TRIM support UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598
2019-03-29 16:13:20 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_aggregate_trim\fR (int)
.ad
.RS 12n
Allow TRIM I/Os to be aggregated. This is normally not helpful because
the extents to be trimmed will have been already been aggregated by the
metaslab. This option is provided for debugging and performance analysis.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_aggregation_limit\fR (int)
.ad
.RS 12n
Max vdev I/O aggregation size
.sp
Add separate aggregation limit for non-rotating media Before sequential scrub patches ZFS never aggregated I/Os above 128KB. Sequential scrub bumped that to 1MB, supposedly to reduce number of head seeks for spinning disks. But for SSDs it makes little to no sense, especially on FreeBSD, where due to MAXPHYS limitation device will likely still see bunch of 128KB I/Os instead of one large. Having more strict aggregation limit for SSDs allows to avoid allocation of large memory buffer and copy to/from it, that is a serious problem when throughput reaches gigabytes per second. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Closes #8494
2019-03-13 19:00:10 +00:00
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_aggregation_limit_non_rotating\fR (int)
.ad
.RS 12n
Max vdev I/O aggregation size for non-rotating media
.sp
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
Default value: \fB131,072\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_bshift\fR (int)
.ad
.RS 12n
Shift size to inflate reads too
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Default value: \fB16\fR (effectively 65536).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_max\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 20:15:10 +00:00
Inflate reads smaller than this value to meet the \fBzfs_vdev_cache_bshift\fR
size (default 64k).
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
.sp
Default value: \fB16384\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_size\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Total size of the per-disk cache in bytes.
.sp
Currently this feature is disabled as it has been found to not be helpful
for performance and in some cases harmful.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 01:47:22 +00:00
\fBzfs_vdev_mirror_rotating_inc\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 01:47:22 +00:00
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O immediately
follows its predecessor on rotational vdevs for the purpose of making decisions
based on load.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 01:47:22 +00:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_rotating_seek_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O lacks
locality as defined by the zfs_vdev_mirror_rotating_seek_offset. I/Os within
this that are not immediately following the previous I/O are incremented by
half.
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_rotating_seek_offset\fR (int)
.ad
.RS 12n
The maximum distance for the last queued I/O in which the balancing algorithm
considers an I/O to have locality.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1048576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_non_rotating_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member on non-rotational vdevs
when I/Os do not immediately follow one another.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_non_rotating_seek_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O lacks
locality as defined by the zfs_vdev_mirror_rotating_seek_offset. I/Os within
this that are not immediately following the previous I/O are incremented by
half.
.sp
Default value: \fB1\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_read_gap_limit\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Aggregate read I/O operations if the gap on-disk between them is within this
threshold.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB32,768\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_write_gap_limit\fR (int)
.ad
.RS 12n
Aggregate write I/O over gap
.sp
Default value: \fB4,096\fR.
.RE
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 08:04:31 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_raidz_impl\fR (string)
.ad
.RS 12n
Fixes and enhancements of SIMD raidz parity - Implementation lock replaced with atomic variable - Trailing whitespace is removed from user specified parameter, to enhance experience when using commands that add newline, e.g. `echo` - raidz_test: remove dependency on `getrusage()` and RUSAGE_THREAD, Issue #4813 - silence `cppcheck` in vdev_raidz, partial solution of Issue #1392 - Minor fixes and cleanups - Enable use of original parity methods in [fastest] configuration. New opaque original ops structure, representing native methods, is added to supported raidz methods. Original parity methods are executed if selected implementation has NULL fn pointer. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4813 Issue #1392
2016-07-17 17:41:11 +00:00
Parameter for selecting raidz parity implementation to use.
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 08:04:31 +00:00
Options marked (always) below may be selected on module load as they are
supported on all systems.
The remaining options may only be set after the module is loaded, as they
are available only if the implementations are compiled in and supported
on the running system.
Once the module is loaded, the content of
/sys/module/zfs/parameters/zfs_vdev_raidz_impl will show available options
with the currently selected one enclosed in [].
Possible options are:
fastest - (always) implementation selected using built-in benchmark
original - (always) original raidz implementation
scalar - (always) scalar raidz implementation
Add RAID-Z routines for SSE2 instruction set, in x86_64 mode. The patch covers low-end and older x86 CPUs. Parity generation is equivalent to SSSE3 implementation, but reconstruction is somewhat slower. Previous 'sse' implementation is renamed to 'ssse3' to indicate highest instruction set used. Benchmark results: scalar_rec_p 4 720476442 scalar_rec_q 4 187462804 scalar_rec_r 4 138996096 scalar_rec_pq 4 140834951 scalar_rec_pr 4 129332035 scalar_rec_qr 4 81619194 scalar_rec_pqr 4 53376668 sse2_rec_p 4 2427757064 sse2_rec_q 4 747120861 sse2_rec_r 4 499871637 sse2_rec_pq 4 522403710 sse2_rec_pr 4 464632780 sse2_rec_qr 4 319124434 sse2_rec_pqr 4 205794190 ssse3_rec_p 4 2519939444 ssse3_rec_q 4 1003019289 ssse3_rec_r 4 616428767 ssse3_rec_pq 4 706326396 ssse3_rec_pr 4 570493618 ssse3_rec_qr 4 400185250 ssse3_rec_pqr 4 377541245 original_rec_p 4 691658568 original_rec_q 4 195510948 original_rec_r 4 26075538 original_rec_pq 4 103087368 original_rec_pr 4 15767058 original_rec_qr 4 15513175 original_rec_pqr 4 10746357 Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4783
2016-06-28 17:49:53 +00:00
sse2 - implementation using SSE2 instruction set (64bit x86 only)
ssse3 - implementation using SSSE3 instruction set (64bit x86 only)
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 08:04:31 +00:00
avx2 - implementation using AVX2 instruction set (64bit x86 only)
Add parity generation/rebuild using AVX-512 for x86-64 avx512f should work on all AVX512 hardware, since it only uses Foundation instructions. avx512bw should be faster on hardware supporting the AVW512BW extension. We can use full-width pshufb (instead of relying on the 256 bits AVX2 pshufb). As a side-effect, the code is also unrolled more. Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.github@dolbeau.name> Closes #5219
2016-11-02 19:40:23 +00:00
avx512f - implementation using AVX512F instruction set (64bit x86 only)
avx512bw - implementation using AVX512F & AVX512BW instruction sets (64bit x86 only)
Add parity generation/rebuild using 128-bits NEON for Aarch64 This re-use the framework established for SSE2, SSSE3 and AVX2. However, GCC is using FP registers on Aarch64, so unlike SSE/AVX2 we can't rely on the registers being left alone between ASM statements. So instead, the NEON code uses C variables and GCC extended ASM syntax. Note that since the kernel explicitly disable vector registers, they have to be locally re-enabled explicitly. As we use the variable's number to define the symbolic name, and GCC won't allow duplicate symbolic names, numbers have to be unique. Even when the code is not going to be used (e.g. the case for 4 registers when using the macro with only 2). Only the actually used variables should be declared, otherwise the build will fails in debug mode. This requires the replacement of the XOR(X,X) syntax by a new ZERO(X) macro, which does the same thing but without repeating the argument. And perhaps someday there will be a machine where there is a more efficient way to zero a register than XOR with itself. This affects scalar, SSE2, SSSE3 and AVX2 as they need the new macro. It's possible to write faster implementations (different scheduling, different unrolling, interleaving NEON and scalar, ...) for various cores, but this one has the advantage of fitting in the current state of the code, and thus is likely easier to review/check/merge. The only difference between aarch64-neon and aarch64-neonx2 is that aarch64-neonx2 unroll some functions some more. Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net> Closes #4801
2016-10-03 16:44:00 +00:00
aarch64_neon - implementation using NEON (Aarch64/64 bit ARMv8 only)
aarch64_neonx2 - implementation using NEON with more unrolling (Aarch64/64 bit ARMv8 only)
Add AltiVec RAID-Z Implements the RAID-Z function using AltiVec SIMD. This is basically the NEON code translated to AltiVec. Note that the 'fletcher' algorithm requires 64-bits operations, and the initial implementations of AltiVec (PPC74xx a.k.a. G4, PPC970 a.k.a. G5) only has up to 32-bits operations, so no 'fletcher'. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.dolbeau@european-processor-initiative.eu> Closes #9539
2020-01-23 19:01:24 +00:00
powerpc_altivec - implementation using Altivec (PowerPC only)
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 08:04:31 +00:00
.sp
Default value: \fBfastest\fR.
.RE
zfs-module-parameters(5): add all missing items I ran a report against the output of `modinfo zfs.ko`. This commit adds everything missing and corrects a few renamed module parameters. Specifically: * zfs_checksums_per second renamed in ad796b8a3 * vdev_ms_count_limit renamed in c853f382d Also fixes some variable type inconsistencies (unsigned int => uint) Reviewed-by: George Amanakis <gamanakis@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #9809
2020-01-07 20:41:53 +00:00
.sp
.ne 2
.na
\fBzfs_vdev_scheduler\fR (charp)
.ad
.RS 12n
\fBDEPRECATED\fR: This option exists for compatibility with older user
configurations. It does nothing except print a warning to the kernel log if
set.
.sp
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzfs_zevent_cols\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
When zevents are logged to the console use this as the word wrap width.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB80\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zevent_console\fR (int)
.ad
.RS 12n
Log events to the console
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_zevent_len_max\fR (int)
.ad
.RS 12n
Don't scale zfs_zevent_len_max by CPU count The lower bound for this scaling to too low and the upper bound is too high. Use a fixed default length of 512 instead, which is a reasonable value on any system. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #11822
2021-03-31 17:56:37 +00:00
Max event queue length.
Events in the queue can be viewed with the \fBzpool events\fR command.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Don't scale zfs_zevent_len_max by CPU count The lower bound for this scaling to too low and the upper bound is too high. Use a fixed default length of 512 instead, which is a reasonable value on any system. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ryan Moeller <ryan@iXsystems.com> Closes #11822
2021-03-31 17:56:37 +00:00
Default value: \fB512\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.sp
.ne 2
Avoid posting duplicate zpool events Duplicate io and checksum ereport events can misrepresent that things are worse than they seem. Ideally the zpool events and the corresponding vdev stat error counts in a zpool status should be for unique errors -- not the same error being counted over and over. This can be demonstrated in a simple example. With a single bad block in a datafile and just 5 reads of the file we end up with a degraded vdev, even though there is only one unique error in the pool. The proposed solution to the above issue, is to eliminate duplicates when posting events and when updating vdev error stats. We now save recent error events of interest when posting events so that we can easily check for duplicates when posting an error. Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Don Brady <don.brady@delphix.com> Closes #10861
2020-09-04 17:34:28 +00:00
.na
\fBzfs_zevent_retain_max\fR (int)
.ad
.RS 12n
Maximum recent zevent records to retain for duplicate checking. Setting
this value to zero disables duplicate detection.
.sp
Default value: \fB2000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zevent_retain_expire_secs\fR (int)
.ad
.RS 12n
Lifespan for a recent ereport that was retained for duplicate checking.
.sp
Default value: \fB900\fR.
.RE
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.na
\fBzfs_zil_clean_taskq_maxalloc\fR (int)
.ad
.RS 12n
The maximum number of taskq entries that are allowed to be cached. When this
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 19:26:32 +00:00
limit is exceeded transaction records (itxs) will be cleaned synchronously.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.sp
Default value: \fB1048576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zil_clean_taskq_minalloc\fR (int)
.ad
.RS 12n
The number of taskq entries that are pre-populated when the taskq is first
created and are immediately available for use.
.sp
Default value: \fB1024\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zil_clean_taskq_nthr_pct\fR (int)
.ad
.RS 12n
This controls the number of threads used by the dp_zil_clean_taskq. The default
value of 100% will create a maximum of one thread per cpu.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 19:51:11 +00:00
Default value: \fB100\fR%.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 19:57:53 +00:00
.RE
make zil max block size tunable We've observed that on some highly fragmented pools, most metaslab allocations are small (~2-8KB), but there are some large, 128K allocations. The large allocations are for ZIL blocks. If there is a lot of fragmentation, the large allocations can be hard to satisfy. The most common impact of this is that we need to check (and thus load) lots of metaslabs from the ZIL allocation code path, causing sync writes to wait for metaslabs to load, which can take a second or more. In the worst case, we may not be able to satisfy the allocation, in which case the ZIL will resort to txg_wait_synced() to ensure the change is on disk. To provide a workaround for this, this change adds a tunable that can reduce the size of ZIL blocks. External-issue: DLPX-61719 Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #8865
2019-06-10 18:48:42 +00:00
.sp
.ne 2
.na
\fBzil_maxblocksize\fR (int)
.ad
.RS 12n
This sets the maximum block size used by the ZIL. On very fragmented pools,
lowering this (typically to 36KB) can improve performance.
.sp
Default value: \fB131072\fR (128KB).
.RE
OpenZFS 9963 - Separate tunable for disabling ZIL vdev flush Porting Notes: * Add options to zfs-module-parameters(5) man page. * zfs_nocacheflush move to vdev.c instead of vdev_disk.c, since the latter doesn't get built for user space. Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Patrick Mooney <patrick.mooney@joyent.com> Reviewed by: Tom Caputi <tcaputi@datto.com> Reviewed by: George Melikov <mail@gmelikov.ru> Approved by: Dan McDonald <danmcd@joyent.com> Ported-by: Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9963 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f8fdf68125 Closes #8186
2018-10-23 16:44:37 +00:00
.sp
.ne 2
.na
\fBzil_nocacheflush\fR (int)
.ad
.RS 12n
Disable the cache flush commands that are normally sent to the disk(s) by
the ZIL after an LWB write has completed. Setting this will cause ZIL
corruption on power loss if a volatile out-of-order write cache is enabled.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzil_replay_disable\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Disable intent logging replay. Can be disabled for recovery from corrupted
ZIL
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 16:15:37 +00:00
\fBzil_slog_bulk\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 16:15:37 +00:00
Limit SLOG write size per commit executed with synchronous priority.
Any writes above that will be executed with lower (asynchronous) priority
to limit potential SLOG device abuse by single active ZIL writer.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 16:15:37 +00:00
Default value: \fB786,432\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.RE
Set aside a metaslab for ZIL blocks Mixing ZIL and normal allocations has several problems: 1. The ZIL allocations are allocated, written to disk, and then a few seconds later freed. This leaves behind holes (free segments) where the ZIL blocks used to be, which increases fragmentation, which negatively impacts performance. 2. When under moderate load, ZIL allocations are of 128KB. If the pool is fairly fragmented, there may not be many free chunks of that size. This causes ZFS to load more metaslabs to locate free segments of 128KB or more. The loading happens synchronously (from zil_commit()), and can take around a second even if the metaslab's spacemap is cached in the ARC. All concurrent synchronous operations on this filesystem must wait while the metaslab is loading. This can cause a significant performance impact. 3. If the pool is very fragmented, there may be zero free chunks of 128KB or more. In this case, the ZIL falls back to txg_wait_synced(), which has an enormous performance impact. These problems can be eliminated by using a dedicated log device ("slog"), even one with the same performance characteristics as the normal devices. This change sets aside one metaslab from each top-level vdev that is preferentially used for ZIL allocations (vdev_log_mg, spa_embedded_log_class). From an allocation perspective, this is similar to having a dedicated log device, and it eliminates the above-mentioned performance problems. Log (ZIL) blocks can be allocated from the following locations. Each one is tried in order until the allocation succeeds: 1. dedicated log vdevs, aka "slog" (spa_log_class) 2. embedded slog metaslabs (spa_embedded_log_class) 3. other metaslabs in normal vdevs (spa_normal_class) The space required for the embedded slog metaslabs is usually between 0.5% and 1.0% of the pool, and comes out of the existing 3.2% of "slop" space that is not available for user data. On an all-ssd system with 4TB storage, 87% fragmentation, 60% capacity, and recordsize=8k, testing shows a ~50% performance increase on random 8k sync writes. On even more fragmented systems (which hit problem #3 above and call txg_wait_synced()), the performance improvement can be arbitrarily large (>100x). Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Don Brady <don.brady@delphix.com> Reviewed-by: Mark Maybee <mark.maybee@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11389
2021-01-21 23:12:54 +00:00
.sp
.ne 2
.na
\fBzfs_embedded_slog_min_ms\fR (int)
.ad
.RS 12n
Usually, one metaslab from each (normal-class) vdev is dedicated for use by
the ZIL (to log synchronous writes).
However, if there are fewer than zfs_embedded_slog_min_ms metaslabs in the
vdev, this functionality is disabled.
This ensures that we don't set aside an unreasonable amount of space for the
ZIL.
.sp
Default value: \fB64\fR.
.RE
zio_deadman_impl() fix and enhancement Add the zio_deadman_log_all tunable to print all zios in zio_deadman_impl(). Also, in all cases, display the depth of the zio relative to the original parent zio. This is meant to be used by developers to gain diagnostic information for hangs which don't involve fully set-up zio trees or are otherwise stuck or hung in an early stage. Reviewed-by: Olaf Faaland <faaland1@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #8362
2019-02-15 20:44:24 +00:00
.sp
.ne 2
.na
\fBzio_deadman_log_all\fR (int)
.ad
.RS 12n
If non-zero, the zio deadman will produce debugging messages (see
\fBzfs_dbgmsg_enable\fR) for all zios, rather than only for leaf
zios possessing a vdev. This is meant to be used by developers to gain
diagnostic information for hang conditions which don't involve a mutex
or other locking primitive; typically conditions in which a thread in
the zio pipeline is looping indefinitely.
.sp
Default value: \fB0\fR.
.RE
OpenZFS 9403 - assertion failed in arc_buf_destroy() Assertion failed in arc_buf_destroy() when concurrently reading block with checksum error. Porting notes: * The ability to zinject decompression errors has been added, but this only works at the zio_decompress() level, where we have all of the info we need to match against the user's zinject options. * The decompress_fault test has been added to test the new zinject functionality * We attempted to set zio_decompress_fail_fraction to (1 << 18) in ztest for further test coverage. Although this did uncover a few low priority issues, this unfortuantely also causes ztest to ASSERT in many locations where the code is working correctly since it is designed to fail on IO errors. Developers can manually set this variable with the '-o' option to find and debug issues. Authored by: Matt Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Matt Ahrens <mahrens@delphix.com> Ported-by: Tom Caputi <tcaputi@datto.com> OpenZFS-issue: https://illumos.org/issues/9403 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/fa98e487a9 Closes #7822
2018-08-29 18:33:33 +00:00
.sp
.ne 2
.na
\fBzio_decompress_fail_fraction\fR (int)
.ad
.RS 12n
If non-zero, this value represents the denominator of the probability that zfs
should induce a decompression failure. For instance, for a 5% decompression
failure rate, this value should be set to 20.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
\fBzio_slow_io_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.ad
.RS 12n
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
When an I/O operation takes more than \fBzio_slow_io_ms\fR milliseconds to
complete is marked as a slow I/O. Each slow I/O causes a delay zevent. Slow
I/O counters can be seen with "zpool status -s".
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB30,000\fR.
.RE
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.sp
.ne 2
.na
\fBzio_dva_throttle_enabled\fR (int)
.ad
.RS 12n
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
Throttle block allocations in the I/O pipeline. This allows for
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
dynamic allocation distribution when devices are imbalanced.
Update documentation for zfs_vdev_queue_depth_pct It was documented as being related to zfs_vdev_async_max_active when it is actually related to zfs_vdev_async_write_max_active. Also, expand the documentation to describe the allocation throttle which was introduced as part of OpenZFS 7090 in 3dfb57a. Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #6064
2017-04-25 04:01:04 +00:00
When enabled, the maximum number of pending allocations per top-level vdev
is limited by \fBzfs_vdev_queue_depth_pct\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.sp
Revert "Disable zio_dva_throttle_enabled by default" Enable zio_dva_throttle_enabled=1 by default. Subsequent testing has been unable to reproduce the suspected regression. Tested-by: kernelOfTruth kerneloftruth@gmail.com Reviewed-by: Olaf Faaland <faaland1@llnl.gov> Signed-off-by: Brian Behlendorf behlendorf1@llnl.gov Reverts #5335 Closes #5289 Closes #5457
2016-12-08 20:57:42 +00:00
Default value: \fB1\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 00:59:18 +00:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzio_requeue_io_start_cut_in_line\fR (int)
.ad
.RS 12n
Prioritize requeued I/O
.sp
Default value: \fB0\fR.
.RE
Make zio_taskq_batch_pct user configurable Adds zio_taskq_batch_pct as an exported module parameter, allowing users to modify it at module load time. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4110
2015-12-16 19:22:32 +00:00
.sp
.ne 2
.na
\fBzio_taskq_batch_pct\fR (uint)
.ad
.RS 12n
Percentage of online CPUs (or CPU cores, etc) which will run a worker thread
Add zpool status -s (slow I/Os) and -p (parseable) This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7756 Closes #6885
2018-11-09 00:47:24 +00:00
for I/O. These workers are responsible for I/O work such as compression and
Make zio_taskq_batch_pct user configurable Adds zio_taskq_batch_pct as an exported module parameter, allowing users to modify it at module load time. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4110
2015-12-16 19:22:32 +00:00
checksum calculations. Fractional number of CPUs will be rounded down.
.sp
The default value of 75 was chosen to avoid using all CPUs which can result in
latency issues and inconsistent application performance, especially when high
compression is enabled.
.sp
Default value: \fB75\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
.ne 2
.na
\fBzvol_inhibit_dev\fR (uint)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Do not create zvol device nodes. This may slightly improve startup time on
systems with a very large number of zvols.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzvol_major\fR (uint)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Major number for zvol block devices
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB230\fR.
.RE
.sp
.ne 2
.na
\fBzvol_max_discard_blocks\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 17:44:46 +00:00
Discard (aka TRIM) operations done on zvols will be done in batches of this
many blocks, where block size is determined by the \fBvolblocksize\fR property
of a zvol.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 06:52:54 +00:00
.sp
Default value: \fB16,384\fR.
.RE
Prefetch start and end of volumes When adding a zvol to the system prefetch zvol_prefetch_bytes from the start and end of the volume. Prefetching these regions of the volume is desirable because they are likely to be accessed immediately by blkid(8), the kernel scanning for a partition table, or another task which probes the devices. Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3659
2015-08-18 20:51:20 +00:00
.sp
.ne 2
.na
\fBzvol_prefetch_bytes\fR (uint)
.ad
.RS 12n
When adding a zvol to the system prefetch \fBzvol_prefetch_bytes\fR
from the start and end of the volume. Prefetching these regions
of the volume is desirable because they are likely to be accessed
immediately by \fBblkid(8)\fR or by the kernel scanning for a partition
table.
.sp
Default value: \fB131,072\fR.
.RE
Reinstate zvol_taskq to fix aio on zvol Commit 37f9dac removed the zvol_taskq for processing zvol requests. This was removed as part of switching to make_request_fn and was motivated by a concern at the time over dispatch latency. However, this also made all bio request synchronous, and caused serious performance issues as the bio submitter would wait for every bio it submitted, effectively making the IO depth 1. This patch reinstate zvol_taskq, and to make sure overlapped I/Os are ordered properly, we take range lock in zvol_request, and pass it along with bio to the I/O functions zvol_{write,discard,read}. In order to facilitate benchmarks a zvol_request_sync module option was added to switch between sync and async request handling. For the moment, the default behavior is synchronous but this is likely to change pending additional testing. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Closes #5824
2017-02-23 00:08:04 +00:00
.sp
.ne 2
.na
\fBzvol_request_sync\fR (uint)
.ad
.RS 12n
When processing I/O requests for a zvol submit them synchronously. This
effectively limits the queue depth to 1 for each I/O submitter. When set
to 0 requests are handled asynchronously by a thread pool. The number of
requests which can be handled concurrently is controller by \fBzvol_threads\fR.
.sp
Default to zvol_request_async=0 Change the default ZVOL behavior so requests are handled asynchronously. This behavior is functionally the same as in the zfs-0.6.4 release. Reviewed-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #5902
2017-05-03 00:37:14 +00:00
Default value: \fB0\fR.
Reinstate zvol_taskq to fix aio on zvol Commit 37f9dac removed the zvol_taskq for processing zvol requests. This was removed as part of switching to make_request_fn and was motivated by a concern at the time over dispatch latency. However, this also made all bio request synchronous, and caused serious performance issues as the bio submitter would wait for every bio it submitted, effectively making the IO depth 1. This patch reinstate zvol_taskq, and to make sure overlapped I/Os are ordered properly, we take range lock in zvol_request, and pass it along with bio to the I/O functions zvol_{write,discard,read}. In order to facilitate benchmarks a zvol_request_sync module option was added to switch between sync and async request handling. For the moment, the default behavior is synchronous but this is likely to change pending additional testing. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Closes #5824
2017-02-23 00:08:04 +00:00
.RE
.sp
.ne 2
.na
\fBzvol_threads\fR (uint)
.ad
.RS 12n
Max number of threads which can handle zvol I/O requests concurrently.
.sp
Default value: \fB32\fR.
.RE
Add port of FreeBSD 'volmode' property The volmode property may be set to control the visibility of ZVOL block devices. This allow switching ZVOL between three modes: full - existing fully functional behaviour (default) dev - hide partitions on ZVOL block devices none - not exposing volumes outside ZFS Additionally the new zvol_volmode module parameter can be used to control the default behaviour. This functionality can be used, for instance, on "backup" pools to avoid cluttering /dev with unneeded zd* devices. Original-patch-by: mav <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: loli10K <ezomori.nozomu@gmail.com> FreeBSD-commit: https://github.com/freebsd/freebsd/commit/dd28e6bb Closes #1796 Closes #3438 Closes #6233
2017-07-12 20:05:37 +00:00
.sp
.ne 2
.na
\fBzvol_volmode\fR (uint)
.ad
.RS 12n
Defines zvol block devices behaviour when \fBvolmode\fR is set to \fBdefault\fR.
Valid values are \fB1\fR (full), \fB2\fR (dev) and \fB3\fR (none).
.sp
Default value: \fB1\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 03:01:20 +00:00
.SH ZFS I/O SCHEDULER
ZFS issues I/O operations to leaf vdevs to satisfy and complete I/Os.
The I/O scheduler determines when and in what order those operations are
issued. The I/O scheduler divides operations into five I/O classes
prioritized in the following order: sync read, sync write, async read,
async write, and scrub/resilver. Each queue defines the minimum and
maximum number of concurrent operations that may be issued to the
device. In addition, the device has an aggregate maximum,
\fBzfs_vdev_max_active\fR. Note that the sum of the per-queue minimums
must not exceed the aggregate maximum. If the sum of the per-queue
maximums exceeds the aggregate maximum, then the number of active I/Os
may reach \fBzfs_vdev_max_active\fR, in which case no further I/Os will
be issued regardless of whether all per-queue minimums have been met.
.sp
For many physical devices, throughput increases with the number of
concurrent operations, but latency typically suffers. Further, physical
devices typically have a limit at which more concurrent operations have no
effect on throughput or can actually cause it to decrease.
.sp
The scheduler selects the next operation to issue by first looking for an
I/O class whose minimum has not been satisfied. Once all are satisfied and
the aggregate maximum has not been hit, the scheduler looks for classes
whose maximum has not been satisfied. Iteration through the I/O classes is
done in the order specified above. No further operations are issued if the
aggregate maximum number of concurrent operations has been hit or if there
are no operations queued for an I/O class that has not hit its maximum.
Every time an I/O is queued or an operation completes, the I/O scheduler
looks for new operations to issue.
.sp
In general, smaller max_active's will lead to lower latency of synchronous
operations. Larger max_active's may lead to higher overall throughput,
depending on underlying storage.
.sp
The ratio of the queues' max_actives determines the balance of performance
between reads, writes, and scrubs. E.g., increasing
\fBzfs_vdev_scrub_max_active\fR will cause the scrub or resilver to complete
more quickly, but reads and writes to have higher latency and lower throughput.
.sp
All I/O classes have a fixed maximum number of outstanding operations
except for the async write class. Asynchronous writes represent the data
that is committed to stable storage during the syncing stage for
transaction groups. Transaction groups enter the syncing state
periodically so the number of queued async writes will quickly burst up
and then bleed down to zero. Rather than servicing them as quickly as
possible, the I/O scheduler changes the maximum number of active async
write I/Os according to the amount of dirty data in the pool. Since
both throughput and latency typically increase with the number of
concurrent operations issued to physical devices, reducing the
burstiness in the number of concurrent operations also stabilizes the
response time of operations from other -- and in particular synchronous
-- queues. In broad strokes, the I/O scheduler will issue more
concurrent operations from the async write queue as there's more dirty
data in the pool.
.sp
Async Writes
.sp
The number of concurrent operations issued for the async write I/O class
follows a piece-wise linear function defined by a few adjustable points.
.nf
| o---------| <-- zfs_vdev_async_write_max_active
^ | /^ |
| | / | |
active | / | |
I/O | / | |
count | / | |
| / | |
|-------o | | <-- zfs_vdev_async_write_min_active
0|_______^______|_________|
0% | | 100% of zfs_dirty_data_max
| |
| `-- zfs_vdev_async_write_active_max_dirty_percent
`--------- zfs_vdev_async_write_active_min_dirty_percent
.fi
Until the amount of dirty data exceeds a minimum percentage of the dirty
data allowed in the pool, the I/O scheduler will limit the number of
concurrent operations to the minimum. As that threshold is crossed, the
number of concurrent operations issued increases linearly to the maximum at
the specified maximum percentage of the dirty data allowed in the pool.
.sp
Ideally, the amount of dirty data on a busy pool will stay in the sloped
part of the function between \fBzfs_vdev_async_write_active_min_dirty_percent\fR
and \fBzfs_vdev_async_write_active_max_dirty_percent\fR. If it exceeds the
maximum percentage, this indicates that the rate of incoming data is
greater than the rate that the backend storage can handle. In this case, we
must further throttle incoming writes, as described in the next section.
.SH ZFS TRANSACTION DELAY
We delay transactions when we've determined that the backend storage
isn't able to accommodate the rate of incoming writes.
.sp
If there is already a transaction waiting, we delay relative to when
that transaction will finish waiting. This way the calculated delay time
is independent of the number of threads concurrently executing
transactions.
.sp
If we are the only waiter, wait relative to when the transaction
started, rather than the current time. This credits the transaction for
"time already served", e.g. reading indirect blocks.
.sp
The minimum time for a transaction to take is calculated as:
.nf
min_time = zfs_delay_scale * (dirty - min) / (max - dirty)
min_time is then capped at 100 milliseconds.
.fi
.sp
The delay has two degrees of freedom that can be adjusted via tunables. The
percentage of dirty data at which we start to delay is defined by
\fBzfs_delay_min_dirty_percent\fR. This should typically be at or above
\fBzfs_vdev_async_write_active_max_dirty_percent\fR so that we only start to
delay after writing at full speed has failed to keep up with the incoming write
rate. The scale of the curve is defined by \fBzfs_delay_scale\fR. Roughly speaking,
this variable determines the amount of delay at the midpoint of the curve.
.sp
.nf
delay
10ms +-------------------------------------------------------------*+
| *|
9ms + *+
| *|
8ms + *+
| * |
7ms + * +
| * |
6ms + * +
| * |
5ms + * +
| * |
4ms + * +
| * |
3ms + * +
| * |
2ms + (midpoint) * +
| | ** |
1ms + v *** +
| zfs_delay_scale ----------> ******** |
0 +-------------------------------------*********----------------+
0% <- zfs_dirty_data_max -> 100%
.fi
.sp
Note that since the delay is added to the outstanding time remaining on the
most recent transaction, the delay is effectively the inverse of IOPS.
Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
was chosen such that small changes in the amount of accumulated dirty data
in the first 3/4 of the curve yield relatively small differences in the
amount of delay.
.sp
The effects can be easier to understand when the amount of delay is
represented on a log scale:
.sp
.nf
delay
100ms +-------------------------------------------------------------++
+ +
| |
+ *+
10ms + *+
+ ** +
| (midpoint) ** |
+ | ** +
1ms + v **** +
+ zfs_delay_scale ----------> ***** +
| **** |
+ **** +
100us + ** +
+ * +
| * |
+ * +
10us + * +
+ +
| |
+ +
+--------------------------------------------------------------+
0% <- zfs_dirty_data_max -> 100%
.fi
.sp
Note here that only as the amount of dirty data approaches its limit does
the delay start to increase rapidly. The goal of a properly tuned system
should be to keep the amount of dirty data out of that range by first
ensuring that the appropriate limits are set for the I/O scheduler to reach
optimal throughput on the backend storage, and then by changing the value
of \fBzfs_delay_scale\fR to increase the steepness of the curve.