Messages in this thread Patch in this message | | | Subject | Re: [RFC][PATCH] sched: Optimize cgroup pick_next_task_fair | From | Mike Galbraith <> | Date | Sat, 11 Feb 2012 07:56:29 +0100 |
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On Sat, 2012-02-11 at 06:05 +0100, Peter Zijlstra wrote: > Since commit 2f36825b1 ("sched: Next buddy hint on sleep and preempt > path") it is likely we pick a new task from the same cgroup, doing a put > and then set on all intermediate entities is a waste of time, so try to > avoid this.
Good idea, we need to lose some weight.
> XXX check put_prev_task()'s update_rq_clock() magic..
I made that even more lovable ;-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d7c4322..7c1cfa6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3175,6 +3175,7 @@ need_resched: } else { deactivate_task(rq, prev, DEQUEUE_SLEEP); prev->on_rq = 0; + rq->skip_clock_update = 1; /* * If a worker went to sleep, notify and ask workqueue @@ -3200,9 +3201,9 @@ need_resched: put_prev_task(rq, prev); next = pick_next_task(rq); clear_tsk_need_resched(prev); - rq->skip_clock_update = 0; if (likely(prev != next)) { + rq->skip_clock_update = 0; rq->nr_switches++; rq->curr = next; ++*switch_count; @@ -3220,6 +3221,7 @@ need_resched: raw_spin_unlock_irq(&rq->lock); post_schedule(rq); + rq->skip_clock_update = 0; preempt_enable_no_resched(); if (need_resched()) > Compile tested only.. inspired by pjt's fast switch stories.
I was looking forward to seeing those fast switch patches, nice spot to cut lard.
> Not-quite-signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
I'll see if I can give it some runtime.
-Mike
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