Commit Graph

73 Commits

Author SHA1 Message Date
DHE 8342673502 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
2016-05-23 11:08:45 -07:00
Richard Laager 1c0120832c 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
2016-03-29 18:33:16 -07:00
smh 9f500936c8 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@e186f564bc by my
  collegue Andriy Gapon has been included. It applied perfectly, but
  added a cstyle regression.
- This replaces 556011dbec 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
2016-02-26 11:24:35 -08:00
Brian Behlendorf 8a09d5fd46 Add l2arc_max_block_size tunable
Set a limit for the largest compressed block which can be written
to an L2ARC device.  By default this limit is set to 16M so there
is no change in behavior.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #4323
2016-02-25 09:44:00 -08:00
kernelOfTruth a966c5640e 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>
2016-01-26 15:26:02 -08:00
George Wilson ba5ad9a48d 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>
2016-01-25 13:15:17 -08:00
Matthew Ahrens 7f60329a26 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>
2016-01-12 09:02:33 -08:00
DHE dcb6bed1df 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
2015-12-18 13:46:23 -08:00
Ned Bass 6b4e21c60e 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
2015-12-18 13:33:37 -08:00
Brian Behlendorf 9965059ab9 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
2015-09-09 14:38:29 -07:00
Brian Behlendorf 3b36f8319d 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
2015-09-04 16:08:14 -07:00
Brian Behlendorf 0500e835af 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
2015-09-04 13:23:53 -07:00
Richard Yao 37f9dac592 zvol processing should use struct bio
Internally, zvols are files exposed through the block device API. This
is intended to reduce overhead when things require block devices.
However, the ZoL zvol code emulates a traditional block device in that
it has a top half and a bottom half. This is an unnecessary source of
overhead that does not exist on any other OpenZFS platform does this.
This patch removes it. Early users of this patch reported double digit
performance gains in IOPS on zvols in the range of 50% to 80%.

Comments in the code suggest that the current implementation was done to
obtain IO merging from Linux's IO elevator. However, the DMU already
does write merging while arc_read() should implicitly merge read IOs
because only 1 thread is permitted to fetch the buffer into ARC. In
addition, commercial ZFSOnLinux distributions report that regular files
are more performant than zvols under the current implementation, and the
main consumers of zvols are VMs and iSCSI targets, which have their own
elevators to merge IOs.

Some minor refactoring allows us to register zfs_request() as our
->make_request() handler in place of the generic_make_request()
function. This eliminates the layer of code that broke IO requests on
zvols into a top half and a bottom half. This has several benefits:

1. No per zvol spinlocks.
2. No redundant IO elevator processing.
3. Interrupts are disabled only when actually necessary.
4. No redispatching of IOs when all taskq threads are busy.
5. Linux's page out routines will properly block.
6. Many autotools checks become obsolete.

An unfortunate consequence of eliminating the layer that
generic_make_request() is that we no longer calls the instrumentation
hooks for block IO accounting. Those hooks are GPL-exported, so we
cannot call them ourselves and consequently, we lose the ability to do
IO monitoring via iostat.  Since zvols are internally files mapped as
block devices, this should be okay. Anyone who is willing to accept the
performance penalty for the block IO layer's accounting could use the
loop device in between the zvol and its consumer. Alternatively, perf
and ftrace likely could be used. Also, tools like latencytop will still
work. Tools such as latencytop sometimes provide a better view of
performance bottlenecks than the traditional block IO accounting tools
do.

Lastly, if direct reclaim occurs during spacemap loading and swap is on
a zvol, this code will deadlock. That deadlock could already occur with
sync=always on zvols. Given that swap on zvols is not yet production
ready, this is not a blocker.

Signed-off-by: Richard Yao <ryao@gentoo.org>
2015-09-04 15:30:24 -04:00
Brian Behlendorf 6cde64351e 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
2015-09-02 09:30:18 -07:00
Andreas Buschmann bba365cfc8 Add extra keyword 'slot' to vdev_id.conf
Add new keyword 'slot' to vdev_id.conf
This selects from where to get the slot number for a SAS/SATA disk
Needed to enable access to the physical position of a disk in a
Supermicro 2027R-AR24NV .

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #3693
2015-08-30 10:03:56 -07:00
Brian Behlendorf 7e8bddd019 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
2015-07-30 11:52:12 -07:00
Brian Behlendorf 11f552fa90 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
2015-07-30 11:50:22 -07:00
Brian Behlendorf 6339c1b9dc Bound zvol_threads module option
The zvol_threads module option should be bounded to a reasonable
range.  The taskq must have at least 1 thread and shouldn't have
more than 1,024 at most.  The default value of 32 is a reasonable
default.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3614
2015-07-29 07:42:11 -07:00
Brian Behlendorf 728d6ae91e 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
2015-07-23 09:42:32 -07:00
Colin Ian King 8f3439733f 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 10:58:31 -07:00
Etienne Dechamps 99b14de421 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>
2015-06-22 14:19:38 -07:00
Prakash Surya ca0bf58d65 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
2015-06-11 10:27:25 -07:00
Turbo Fredriksson d050c627b5 Improve on the ZFS events documentation
* Add information about the 'zpool events' command in zpool(8).
* More events and payloads defined in zfs-events(5).
* I/O Stages and I/O Flags sections added.
* Remove unused legacy "zio_deadline" payload define.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3467
2015-06-09 11:19:19 -07:00
Matthew Ahrens f1512ee61e 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
2015-05-11 12:23:16 -07:00
Jerry Jelinek 788eb90c4c Illumos 3897 - zfs filesystem and snapshot limits
3897 zfs filesystem and snapshot limits
Author: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://www.illumos.org/issues/3897
  https://github.com/illumos/illumos-gate/commit/a2afb61

Porting Notes:

dsl_dataset_snapshot_check(): reduce stack usage using kmem_alloc().

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-04-28 16:22:51 -07:00
cburroughs 7008109646 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 14:58:38 -07:00
Brian Behlendorf 74aa2ba259 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 11:55:28 -07:00
George Wilson b738bc5a0f 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 15:02:50 -07:00
Isaac Huang e89bd69775 zio_injection_enabled should not be a module option
The zio_inject.c keeps zio_injection_enabled as a counter of
fault handlers, so it should not be exported to user space as
a module option.

Several EXPORT_SYMBOLs are moved from zio.c to zio_inject.c,
where the symbols are defined.

Signed-off-by: Isaac Huang <he.huang@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3199
2015-03-24 13:22:03 -07:00
Brian Behlendorf bc88866657 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
2015-03-20 10:35:20 -07:00
Brian Behlendorf 2cbb06b561 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
2015-03-20 10:35:20 -07:00
Brian Behlendorf 6442f3cfe3 Retire zio_bulk_flags
Long ago the zio_bulk_flags module parameter was introduced to
facilitate debugging and profiling the zio_buf_caches.  Today
this code works well and there's no compelling reason to keep
this functionality.  In fact it's preferable to revert this so
the code is more consistent with other ZFS implementations.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Issue #3063
2015-02-10 16:08:49 -08:00
Ned Bass 33b6dbbc51 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
2015-01-07 15:50:49 -08:00
Daniil Lunev 62bdd5eb7a Illumos 4924 - LZ4 Compression for metadata
Reviewed by Matthew Ahrens <mahrens@delphix.com>
Reviewed by Saso Kiselkov <skiselkov.ml@gmail.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://github.com/illumos/illumos-gate/commit/b8289d2
  https://www.illumos.org/issues/3756

Porting notes:

The static function zfs_prop_activate_feature() was removed because
this change removes the only caller.  The function was not removed
from Illumos but instead left as dead code.  However, to keep gcc
happy it was removed from Linux and may be easily restored if needed.

Ported by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1540
2014-10-20 16:17:49 -07:00
Max Grossman 36283ca233 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
2014-09-23 14:26:34 -07:00
Matthew Ahrens b8bcca18f7 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
2014-09-23 10:00:02 -07:00
Alexey Smirnoff 0dfc732416 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
2014-09-04 09:50:45 -07:00
Matthew Ahrens dea377c0d9 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
2014-08-26 16:29:57 -07:00
Matthew Ahrens 49ddb31506 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
2014-08-26 16:14:49 -07:00
George Wilson f3a7f6610f 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
2014-08-18 08:40:49 -07:00
Matthew Ahrens fbeddd60b7 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
2014-08-04 11:50:52 -07:00
Matthew Ahrens 9b67f60560 Illumos 4757, 4913
4757 ZFS embedded-data block pointers ("zero block compression")
4913 zfs release should not be subject to space checks

Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/4757
  https://www.illumos.org/issues/4913
  https://github.com/illumos/illumos-gate/commit/5d7b4d4

Porting notes:

For compatibility with the fastpath code the zio_done() function
needed to be updated.  Because embedded-data block pointers do
not require DVAs to be allocated the associated vdevs will not
be marked and therefore should not be unmarked.

Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2544
2014-08-01 14:28:05 -07:00
Matthew Ahrens da536844d5 Illumos 4368, 4369.
4369 implement zfs bookmarks
4368 zfs send filesystems from readonly pools
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/4369
  https://www.illumos.org/issues/4368
  https://github.com/illumos/illumos-gate/commit/78f1710

Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2530
2014-07-29 10:55:29 -07:00
Max Grossman b0bc7a84d9 Illumos 4370, 4371
4370 avoid transmitting holes during zfs send
4371 DMU code clean up

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: Garrett D'Amore <garrett@damore.org>a

References:
  https://www.illumos.org/issues/4370
  https://www.illumos.org/issues/4371
  https://github.com/illumos/illumos-gate/commit/43466aa

Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2529
2014-07-28 14:29:58 -07:00
Matthew Ahrens fa86b5dbb6 Illumos 4171, 4172
4171 clean up spa_feature_*() interfaces
4172 implement extensible_dataset feature for use by other zpool features

Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Approved by: Garrett D'Amore <garrett@damore.org>a

References:
  https://www.illumos.org/issues/4171
  https://www.illumos.org/issues/4172
  https://github.com/illumos/illumos-gate/commit/2acef22

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2528
2014-07-25 16:40:07 -07:00
Turbo Fredriksson a60e668bd2 Initial attempt to document events and payloads.
In no way complete - most have been trial and error and some
deducing what they could mean. It needs more information from
someone that knows the code better. But this is a start and
it lays the basic structure for adding this additional detail.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2357
2014-07-25 11:58:36 -07:00
George Wilson 93cf20764a Illumos #4101, #4102, #4103, #4105, #4106
4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>

Prior to this patch, space_maps were preferred solely based on the
amount of free space left in each. Unfortunately, this heuristic didn't
contain any information about the make-up of that free space, which
meant we could keep preferring and loading a highly fragmented space map
that wouldn't actually have enough contiguous space to satisfy the
allocation; then unloading that space_map and repeating the process.

This change modifies the space_map's to store additional information
about the contiguous space in the space_map, so that we can use this
information to make a better decision about which space_map to load.
This requires reallocating all space_map objects to increase their
bonus buffer size sizes enough to fit the new metadata.

The above feature can be enabled via a new feature flag introduced by
this change: com.delphix:spacemap_histogram

In addition to the above, this patch allows the space_map block size to
be increase. Currently the block size is set to be 4K in size, which has
certain implications including the following:

    * 4K sector devices will not see any compression benefit
    * large space_maps require more metadata on-disk
    * large space_maps require more time to load (typically random reads)

Now the space_map block size can adjust as needed up to the maximum size
set via the space_map_max_blksz variable.

A bug was fixed which resulted in potentially leaking an object when
removing a mirrored log device. The previous logic for vdev_remove() did
not deal with removing top-level vdevs that are interior vdevs (i.e.
mirror) correctly. The problem would occur when removing a mirrored log
device, and result in the DTL space map object being leaked; because
top-level vdevs don't have DTL space map objects associated with them.

References:
  https://www.illumos.org/issues/4101
  https://www.illumos.org/issues/4102
  https://www.illumos.org/issues/4103
  https://www.illumos.org/issues/4105
  https://www.illumos.org/issues/4106
  https://github.com/illumos/illumos-gate/commit/0713e23

Porting notes:

A handful of kmem_alloc() calls were converted to kmem_zalloc(). Also,
the KM_PUSHPAGE and TQ_PUSHPAGE flags were used as necessary.

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2488
2014-07-22 09:39:16 -07:00
Tim Chase f4a4046bd6 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 ac72fac3ea.  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
2014-07-16 16:49:25 -07:00
Tim Chase 27b293be8a 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
2014-06-06 13:04:43 -07:00
George Wilson aa7d06a98a 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
2014-05-06 09:46:04 -07:00