Messages in this thread | | | Subject | Re: [PATCH] sched/fair: Optimize dequeue_task_fair() | From | Peng Wang <> | Date | Tue, 16 Jun 2020 14:09:39 +0800 |
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On 6/15/20 11:09 PM, Vincent Guittot wrote: > On Mon, 15 Jun 2020 at 16:20, Peng Wang <rocking@linux.alibaba.com> wrote: >> >> While looking at enqueue_task_fair and dequeue_task_fair, it occurred >> to me that dequeue_task_fair can also be optimized as Vincent described >> in commit 7d148be69e3a ("sched/fair: Optimize enqueue_task_fair()"). > > good point > >> >> dequeue_throttle label can ensure se not to be NULL, and se is >> always NULL when reaching root level. >> >> Signed-off-by: Peng Wang <rocking@linux.alibaba.com> >> --- >> kernel/sched/fair.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index cbcb2f7..e6be952 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5614,10 +5614,10 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) >> >> } >> >> -dequeue_throttle: >> - if (!se) >> - sub_nr_running(rq, 1); >> + /* At this point se is NULL and we are at root level*/ >> + sub_nr_running(rq, 1); >> >> +dequeue_throttle: >> /* balance early to pull high priority tasks */ >> if (unlikely(!was_sched_idle && sched_idle_rq(rq))) >> rq->next_balance = jiffies; > > You can move the label here because sched_idle_rq() uses > rq->nr-running and rq->cfs.idle_h_nr_running so they will not change > if we jump to the label before reaching root level
Yes, then we can also skip the early balance check.
> >> -- >> 2.9.5 >>
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