The following commit has been merged into the sched/core branch of tip: Commit-ID: 423d02e1463b21109106f52d94f7396b63731f3b Gitweb: https://git.kernel.org/tip/423d02e1463b21109106f52d94f7396b63731f3b Author: Peng Wang <rocking@xxxxxxxxxxxxxxxxx> AuthorDate: Tue, 16 Jun 2020 14:04:07 +08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Thu, 25 Jun 2020 13:45:44 +02:00 sched/fair: Optimize dequeue_task_fair() 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()"). When encountering throttled cfs_rq, dequeue_throttle label can ensure se not to be NULL, and rq->nr_running remains unchanged, so we can also skip the early balance check. Signed-off-by: Peng Wang <rocking@xxxxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Link: https://lkml.kernel.org/r/701eef9a40de93dcf5fe7063fd607bca5db38e05.1592287263.git.rocking@xxxxxxxxxxxxxxxxx --- 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 a63f400..b9b9f19 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5624,14 +5624,14 @@ 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); /* balance early to pull high priority tasks */ if (unlikely(!was_sched_idle && sched_idle_rq(rq))) rq->next_balance = jiffies; +dequeue_throttle: util_est_dequeue(&rq->cfs, p, task_sleep); hrtick_update(rq); }
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