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| author | john stultz <johnstul@us.ibm.com> | 2007-10-16 23:27:18 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-17 08:42:53 -0700 |
| commit | b2d9323d139f5c384fa1ef1d74773b4db1c09b3d (patch) | |
| tree | ad2705044b5b781aeb1a119d9c8548a044c7e21f | |
| parent | 3075d9da0b4ccc88959db30de80ebd11d2dde175 (diff) | |
| download | linux-b2d9323d139f5c384fa1ef1d74773b4db1c09b3d.tar.gz linux-b2d9323d139f5c384fa1ef1d74773b4db1c09b3d.tar.bz2 linux-b2d9323d139f5c384fa1ef1d74773b4db1c09b3d.zip | |
Use num_possible_cpus() instead of NR_CPUS for timer distribution
To avoid lock contention, we distribute the sched_timer calls across the
cpus so they do not trigger at the same instant. However, I used NR_CPUS,
which can cause needless grouping on small smp systems depending on your
kernel config. This patch converts to using num_possible_cpus() so we
spread it as evenly as possible on every machine.
Briefly tested w/ NR_CPUS=255 and verified reduced contention.
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/time/tick-sched.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 8c3fef1db09c..ce89ffb474d0 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -570,7 +570,7 @@ void tick_setup_sched_timer(void) /* Get the next period (per cpu) */ ts->sched_timer.expires = tick_init_jiffy_update(); offset = ktime_to_ns(tick_period) >> 1; - do_div(offset, NR_CPUS); + do_div(offset, num_possible_cpus()); offset *= smp_processor_id(); ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset); |