RE: [PATCH] sched/fair: don't use waker's cpu if the waker of sync wake-up is interrupt

-----Original Message-----
From: Mike Galbraith [mailto:efault@gmx.de]
Sent: Tuesday, April 27, 2021 5:55 PM
To: Song Bao Hua (Barry Song) <redacted>;
vincent.guittot@linaro.org; mingo@redhat.com; peterz@infradead.org;
dietmar.eggemann@arm.com; rostedt@goodmis.org; bsegall@google.com;
mgorman@suse.de
Cc: valentin.schneider@arm.com; juri.lelli@redhat.com; bristot@redhat.com;
linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; xuwei (O)
[off-list ref]; Zengtao (B) [off-list ref];
guodong.xu@linaro.org; yangyicong [off-list ref]; Liguozhu (Kenneth)
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[off-list ref]; xieyongjia (A) [off-list ref]
Subject: Re: [PATCH] sched/fair: don't use waker's cpu if the waker of sync
wake-up is interrupt

On Tue, 2021-04-27 at 04:44 +0000, Song Bao Hua (Barry Song) wrote:

quoted

I agree sync hint might have been overused by other kernel subsystem.
But this patch will at least fix a case: sync waker is interrupt,
in this case, the existing task has nothing to do with waker and wakee,
so this case should be excluded from wake_affine_idle().

I long ago tried filtering interrupt wakeups, and met some surprises.
Wakeup twiddling always managing to end up being a rob Peter to pay
Paul operation despite our best efforts, here's hoping that your pile
of stolen cycles is small enough to escape performance bot notice :)

Would you like to share the link you did before to filter interrupt
wakeups?

The wake up path has hundreds of lines of code, so I don't expect that
reading preempt_count will cause visible performance losses to bot. But
who knows :-)

	-Mike

Thanks
Barry

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