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author | Nicolai Hähnle <Nicolai.Haehnle@amd.com> | 2016-12-21 19:46:38 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2017-01-14 11:14:52 +0100 |
commit | c516df978df1471793aaa4809b390ecd40fa93c2 (patch) | |
tree | 9289e5433efe2bf899d1c1a4ce8e56b5de4de8c4 /fs/afs/main.c | |
parent | locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop (diff) | |
download | linux-c516df978df1471793aaa4809b390ecd40fa93c2.tar.xz linux-c516df978df1471793aaa4809b390ecd40fa93c2.zip |
locking/ww_mutex: Optimize ww-mutexes by yielding to other waiters from optimistic spin
Lock stealing is less beneficial for w/w mutexes since we may just end up
backing off if we stole from a thread with an earlier acquire stamp that
already holds another w/w mutex that we also need. So don't spin
optimistically unless we are sure that there is no other waiter that might
cause us to back off.
Median timings taken of a contention-heavy GPU workload:
Before:
real 0m52.946s
user 0m7.272s
sys 1m55.964s
After:
real 0m53.086s
user 0m7.360s
sys 1m46.204s
This particular workload still spends 20%-25% of CPU in mutex_spin_on_owner
according to perf, but my attempts to further reduce this spinning based on
various heuristics all lead to an increase in measured wall time despite
the decrease in sys time.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-11-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'fs/afs/main.c')
0 files changed, 0 insertions, 0 deletions