Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=3704540b48295253bd9c87a5e7ff545f9d47a3b8
Commit: 3704540b48295253bd9c87a5e7ff545f9d47a3b8
Parent: 5590a536c0bc403fc73908c66c1c88cbed735ecb
Author: john stultz <[EMAIL PROTECTED]>
AuthorDate: Sat Jul 21 04:37:35 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Sat Jul 21 17:49:15 2007 -0700
tick management: spread timer interrupt
After discussing w/ Thomas over IRC, it seems the issue is the sched tick
fires on every cpu at the same time, causing extra lock contention.
This smaller change, adds an extra offset per cpu so the ticks don't line
up.
This patch also drops the idle latency from 40us down to under 20us.
Signed-off-by: john stultz <[EMAIL PROTECTED]>
Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
Cc: Ingo Molnar <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
kernel/time/tick-sched.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 52db9e3..b416995 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -546,6 +546,7 @@ void tick_setup_sched_timer(void)
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
ktime_t now = ktime_get();
+ u64 offset;
/*
* Emulate tick processing via per-CPU hrtimers:
@@ -554,8 +555,12 @@ void tick_setup_sched_timer(void)
ts->sched_timer.function = tick_sched_timer;
ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
- /* Get the next period */
+ /* 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);
+ offset *= smp_processor_id();
+ ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset);
for (;;) {
hrtimer_forward(&ts->sched_timer, now, tick_period);
-
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