From b2d9323d139f5c384fa1ef1d74773b4db1c09b3d Mon Sep 17 00:00:00 2001 From: john stultz Date: Tue, 16 Oct 2007 23:27:18 -0700 Subject: 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 --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 8c3fef1..ce89ffb 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); -- cgit v1.1