Messages in this thread Patch in this message | | | From | Morten Rasmussen <> | Subject | [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in wake_wide | Date | Mon, 23 May 2016 11:58:45 +0100 |
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wake_wide() is based on task wakee_flips of the waker and the wakee to decide whether an affine wakeup is desirable. On lightly loaded systems the waker is frequently the idle task (pid=0) which can accumulate a lot of wakee_flips in that scenario. It makes little sense to prevent affine wakeups on an idle cpu due to the idle task wakee_flips, so it makes more sense to ignore them in wake_wide().
cc: Ingo Molnar <mingo@redhat.com> cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> --- kernel/sched/fair.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c49e25a..0fe3020 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5007,6 +5007,10 @@ static int wake_wide(struct task_struct *p) unsigned int slave = p->wakee_flips; int factor = this_cpu_read(sd_llc_size); + /* Don't let the idle task prevent affine wakeups */ + if (is_idle_task(current)) + return 0; + if (master < slave) swap(master, slave); if (slave < factor || master < slave * factor) -- 1.9.1
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