linux-kernel - Re: [PATCH v3 1/2] sched/fair: Introduce short duration task check

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Message-ID: <Y5CiN010QAwklahh@chenyu5-mobl1>
Date:   Wed, 7 Dec 2022 22:24:55 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Josh Don <joshdon@...gle.com>
CC:     Vincent Guittot <vincent.guittot@...aro.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Honglei Wang <wanghonglei@...ichuxing.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        "Rik van Riel" <riel@...riel.com>, Aaron Lu <aaron.lu@...el.com>,
        Abel Wu <wuyun.abel@...edance.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        "Yicong Yang" <yangyicong@...ilicon.com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Hillf Danton <hdanton@...a.com>,
        Len Brown <len.brown@...el.com>,
        Chen Yu <yu.chen.surf@...il.com>,
        "Tianchen Ding" <dtcccc@...ux.alibaba.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] sched/fair: Introduce short duration task check

Hi Josh,
On 2022-12-06 at 18:23:47 -0800, Josh Don wrote:
> > We don't want to add more dedicated knobs. So using
> > sysctl_sched_min_granularity as you are doing in this patch looks ok
> 
> If not a knob, then maybe at least a smaller hardcoded value? Several
> milliseconds seems like too long for this optimization; the
> opportunity cost of not doing the idle search likely doesn't make
> sense if the waker is going to be active for several additional
> milliseconds. I would have guessed something on the order of 100us.
> 
> Chen, what is the run duration of tasks in your ping pong example?
OK, I'll measure the duration of all the tests and summarize the data later.

thanks,
Chenyu