On Mon, 15 Jun 2020 at 16:20, Peng Wang <rock...@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 <rock...@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 > -- > 2.9.5 >
