Commit 7c2e8bbd authored Dec 03, 2019 by Frederic Weisbecker Committed by Peter Zijlstra Dec 17, 2019

sched: Spare resched IPI when prio changes on a single fair task



The runqueue of a fair task being remotely reniced is going to get a
resched IPI in order to reassess which task should be the current
running on the CPU. However that evaluation is useless if the fair task
is running alone, in which case we can spare that IPI, preventing
nohz_full CPUs from being disturbed.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20191203160106.18806-2-frederic@kernel.org

parent 025f50f3

kernel/sched/fair.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -10322,6 +10322,9 @@ prio_changed_fair(struct rq rq, struct task_struct p, int oldprio)
		if (!task_on_rq_queued(p))
		return;

		if (rq->cfs.nr_running == 1)
		return;

		/*
		* Reschedule if we are currently running on this runqueue and
		* our priority decreased, or if we are not currently running on

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