OpenZFS on Linux and FreeBSD
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George Amanakis 085321621e
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 10:10:44 -07:00
.github Remove 'ZFS on Linux' references from PR Template 2020-09-03 16:31:05 -07:00
cmd Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
config config/zfs-build.m4: never define _initramfs in RPM_DEFINE_UTIL 2020-09-12 08:22:07 -07:00
contrib Remove vestigial settings related to initramfs 2020-08-22 11:04:49 -07:00
etc Fix another dependency loop 2020-08-28 10:17:14 -07:00
include Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
lib libzutil depends on libnvpair 2020-09-12 08:19:48 -07:00
man Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
module Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
rpm Use correct prefix for share/pam-configs 2020-07-30 09:09:46 -07:00
scripts Add a missing option prefix `-` in zfs-tests.sh usage() 2020-09-08 09:04:36 -07:00
tests Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
udev Centralize variable substitution 2020-07-14 17:33:44 -07:00
.editorconfig Add an .editorconfig; document git whitespace settings 2020-01-27 13:32:52 -08:00
.gitignore Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
.gitmodules Add zimport.sh compatibility test script 2014-02-21 12:10:31 -08:00
AUTHORS Add zstd support to zfs 2020-08-20 10:30:06 -07:00
CODE_OF_CONDUCT.md Add CODE_OF_CONDUCT.md 2019-04-30 10:58:45 -07:00
COPYRIGHT Fix typos 2020-06-09 21:24:09 -07:00
LICENSE Update build system and packaging 2018-05-29 16:00:33 -07:00
META Tag 2.0.0-rc1 2020-08-25 13:11:25 -07:00
Makefile.am Silence 'make checkbashisms' 2020-08-20 13:45:47 -07:00
NEWS Fix NEWS file 2020-08-26 21:44:41 -07:00
NOTICE Update build system and packaging 2018-05-29 16:00:33 -07:00
README.md Update wiki links with new address 2020-06-03 19:46:31 -07:00
TEST Remove CI builder customization from TEST 2020-03-16 10:46:03 -07:00
autogen.sh Cause autogen.sh to fail if autoreconf fails 2018-07-06 09:27:37 -07:00
configure.ac Add L2ARC arcstats for MFU/MRU buffers and buffer content type 2020-09-14 10:10:44 -07:00
copy-builtin Move zfs_gitrev.h to build directory 2020-06-24 18:19:28 -07:00
cppcheck-suppressions.txt Import ZStandard v1.4.5 2020-08-20 10:30:06 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

README.md

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OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.

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Official Resources

Installation

Full documentation for installing OpenZFS on your favorite Linux distribution can be found at the ZoL Site.

Contribute & Develop

We have a separate document with contribution guidelines.

We have a Code of Conduct.

Release

OpenZFS is released under a CDDL license. For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are 12-STABLE and 13-CURRENT.