From: john stultz Date: Wed, 17 Oct 2007 06:27:18 +0000 (-0700) Subject: Use num_possible_cpus() instead of NR_CPUS for timer distribution X-Git-Tag: v2.6.24-rc1~679 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b2d9323d139f5c384fa1ef1d74773b4db1c09b3d;p=linux-2.6 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 Acked-by: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 8c3fef1db0..ce89ffb474 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);