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H A Dverity.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A DKconfigdiff 7f8e249dccc4c530cf26c2c091f5bb64e701c262 Thu Mar 03 15:21:27 CST 2022 Jaegeuk Kim <jaegeuk@kernel.org> f2fs: introduce F2FS_UNFAIR_RWSEM to support unfair rwsem

Unfair rwsem should be used when blk-cg is on. Otherwise, there is regression.

FYI, we noticed a -26.7% regression of aim7.jobs-per-min due to commit:

commit: e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae ("f2fs: move f2fs to use reader-unfair rwsems")
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master

in testcase: aim7
on test machine: 88 threads 2 sockets Intel(R) Xeon(R) Gold 6238M CPU @ 2.10GHz with 128G memory
with following parameters:

disk: 4BRD_12G
md: RAID0
fs: f2fs
test: sync_disk_rw
load: 100
cpufreq_governor: performance
ucode: 0x500320a

test-description: AIM7 is a traditional UNIX system level benchmark suite which is used to test and measure the performance of multiuser system.
test-url: https://sourceforge.net/projects/aimbench/files/aim-suite7/

Reported-by: kernel test robot <oliver.sang@intel.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dcompress.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dsysfs.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dinline.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dxattr.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Drecovery.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Ddir.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dnamei.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dgc.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Df2fs.hdiff 7f8e249dccc4c530cf26c2c091f5bb64e701c262 Thu Mar 03 15:21:27 CST 2022 Jaegeuk Kim <jaegeuk@kernel.org> f2fs: introduce F2FS_UNFAIR_RWSEM to support unfair rwsem

Unfair rwsem should be used when blk-cg is on. Otherwise, there is regression.

FYI, we noticed a -26.7% regression of aim7.jobs-per-min due to commit:

commit: e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae ("f2fs: move f2fs to use reader-unfair rwsems")
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master

in testcase: aim7
on test machine: 88 threads 2 sockets Intel(R) Xeon(R) Gold 6238M CPU @ 2.10GHz with 128G memory
with following parameters:

disk: 4BRD_12G
md: RAID0
fs: f2fs
test: sync_disk_rw
load: 100
cpufreq_governor: performance
ucode: 0x500320a

test-description: AIM7 is a traditional UNIX system level benchmark suite which is used to test and measure the performance of multiuser system.
test-url: https://sourceforge.net/projects/aimbench/files/aim-suite7/

Reported-by: kernel test robot <oliver.sang@intel.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dcheckpoint.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dnode.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dsegment.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dsuper.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Ddata.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
H A Dfile.cdiff e4544b63a7ee49e7fbebf35ece0a6acd3b9617ae Fri Jan 07 14:48:44 CST 2022 Tim Murray <timmurray@google.com> f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>