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

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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.

Link: https://lkml.kernel.org/r/20191203160106.18806-2-frederic@kernel.org
Change-Id: I7fc11e9b48643f0a4cb73838028c1b556cd79dbb
Cc: Ingo Molnar <mingo@kernel.org>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Yaroslav Furman <yaro330@gmail.com>
Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>
This commit is contained in:
Frederic Weisbecker 2019-12-03 17:01:05 +01:00 committed by Richard Raya
parent d02797647d
commit fff2a8b926
1 changed files with 3 additions and 0 deletions
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3
kernel/sched/fair.c
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@ -12500,6 +12500,9 @@ 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