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sched/fair: Optimize dequeue_task_fair()

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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 7d148be69e ("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@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/701eef9a40de93dcf5fe7063fd607bca5db38e05.1592287263.git.rocking@linux.alibaba.com
This commit is contained in:
Peng Wang 2020-06-16 14:04:07 +08:00 committed by Peter Zijlstra
parent aa93cd53bc
commit 423d02e146
1 changed files with 3 additions and 3 deletions
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6
kernel/sched/fair.c
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@ -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);
}