Commit 8e1ac429 authored Nov 12, 2020 by Quentin Perret Committed by Peter Zijlstra Nov 17, 2020

sched/fair: Fix overutilized update in enqueue_task_fair()



enqueue_task_fair() attempts to skip the overutilized update for new
tasks as their util_avg is not accurate yet. However, the flag we check
to do so is overwritten earlier on in the function, which makes the
condition pretty much a nop.

Fix this by saving the flag early on.

Fixes: 2802bf3c ("sched/fair: Add over-utilization/tipping point indicator")
Reported-by: Rick Yiu <rickyiu@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20201112111201.2081902-1-qperret@google.com

parent 8d4d9c7b

kernel/sched/fair.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5477,6 +5477,7 @@ enqueue_task_fair(struct rq rq, struct task_struct p, int flags)
		struct cfs_rq *cfs_rq;
		struct sched_entity *se = &p->se;
		int idle_h_nr_running = task_has_idle_policy(p);
		int task_new = !(flags & ENQUEUE_WAKEUP);

		/*
		* The code below (indirectly) updates schedutil which looks at
		@@ -5549,7 +5550,7 @@ enqueue_task_fair(struct rq rq, struct task_struct p, int flags)
		* into account, but that is not straightforward to implement,
		* and the following generally works well enough in practice.
		*/
		if (flags & ENQUEUE_WAKEUP)
		if (!task_new)
		update_overutilized_status(rq);

		enqueue_throttle:

Admin message