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

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Message-ID: <6c91195a6de9423abc78e8f85efc2780@hisilicon.com>
Date:   Tue, 27 Apr 2021 06:05:09 +0000
From:   "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
To:     Mike Galbraith <efault@....de>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "bsegall@...gle.com" <bsegall@...gle.com>,
        "mgorman@...e.de" <mgorman@...e.de>
CC:     "valentin.schneider@....com" <valentin.schneider@....com>,
        "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
        "bristot@...hat.com" <bristot@...hat.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xuwei (O)" <xuwei5@...wei.com>,
        "Zengtao (B)" <prime.zeng@...ilicon.com>,
        "guodong.xu@...aro.org" <guodong.xu@...aro.org>,
        yangyicong <yangyicong@...wei.com>,
        "Liguozhu (Kenneth)" <liguozhu@...ilicon.com>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>,
        wanghuiqiang <wanghuiqiang@...wei.com>,
        "xieyongjia (A)" <xieyongjia1@...wei.com>
Subject: 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@....de]
> Sent: Tuesday, April 27, 2021 5:55 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@...ilicon.com>;
> vincent.guittot@...aro.org; mingo@...hat.com; peterz@...radead.org;
> dietmar.eggemann@....com; rostedt@...dmis.org; bsegall@...gle.com;
> mgorman@...e.de
> Cc: valentin.schneider@....com; juri.lelli@...hat.com; bristot@...hat.com;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; xuwei (O)
> <xuwei5@...wei.com>; Zengtao (B) <prime.zeng@...ilicon.com>;
> guodong.xu@...aro.org; yangyicong <yangyicong@...wei.com>; Liguozhu (Kenneth)
> <liguozhu@...ilicon.com>; linuxarm@...neuler.org; wanghuiqiang
> <wanghuiqiang@...wei.com>; xieyongjia (A) <xieyongjia1@...wei.com>
> 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:
> >
> >
> > 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