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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2011-04-05 17:23:58 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-04-14 08:52:41 +0200 |
| commit | 317f394160e9beb97d19a84c39b7e5eb3d7815a8 (patch) | |
| tree | 486f268e9ec010744c17333f0f543da9d3909ff4 /kernel/sched_features.h | |
| parent | c05fbafba1c5482bee399b360288fa405415e126 (diff) | |
| download | linux-317f394160e9beb97d19a84c39b7e5eb3d7815a8.tar.bz2 | |
sched: Move the second half of ttwu() to the remote cpu
Now that we've removed the rq->lock requirement from the first part of
ttwu() and can compute placement without holding any rq->lock, ensure
we execute the second half of ttwu() on the actual cpu we want the
task to run on.
This avoids having to take rq->lock and doing the task enqueue
remotely, saving lots on cacheline transfers.
As measured using: http://oss.oracle.com/~mason/sembench.c
$ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance > $i; done
$ echo 4096 32000 64 128 > /proc/sys/kernel/sem
$ ./sembench -t 2048 -w 1900 -o 0
unpatched: run time 30 seconds 647278 worker burns per second
patched: run time 30 seconds 816715 worker burns per second
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110405152729.515897185@chello.nl
Diffstat (limited to 'kernel/sched_features.h')
| -rw-r--r-- | kernel/sched_features.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/sched_features.h b/kernel/sched_features.h index 68e69acc29b9..be40f7371ee1 100644 --- a/kernel/sched_features.h +++ b/kernel/sched_features.h @@ -64,3 +64,9 @@ SCHED_FEAT(OWNER_SPIN, 1) * Decrement CPU power based on irq activity */ SCHED_FEAT(NONIRQ_POWER, 1) + +/* + * Queue remote wakeups on the target CPU and process them + * using the scheduler IPI. Reduces rq->lock contention/bounces. + */ +SCHED_FEAT(TTWU_QUEUE, 1) |