linux-kernel - Re: [External] Re: Subject: [PATCH] sched/fair: prioritize normal task over sched

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Message-ID: <5de97c7f-2c71-34d0-9443-27f71960b4dd@bytedance.com>
Date:   Tue, 15 Mar 2022 10:04:55 +0800
From:   chenying <chenying.kernel@...edance.com>
To:     Josh Don <joshdon@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Benjamin Segall <bsegall@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        duanxiongchun@...edance.com, zhouchengming@...edance.com,
        songmuchun@...edance.com, zhengqi.arch@...edance.com,
        zhoufeng.zf@...edance.com, ligang.bdlg@...edance.com
Subject: Re: [External] Re: Subject: [PATCH] sched/fair: prioritize normal
 task over sched_idle task with vruntime offset

在 2022/3/15 8:30, Josh Don 写道:
> On Sun, Mar 13, 2022 at 3:07 AM chenying <chenying.kernel@...edance.com> wrote:
>>
>> If I set the sched_idle_vruntime_offset to a relatively small value
>> (e.g. 10 minutes), can this issues be avoided?
> 
> That's still long enough to cause lockups.
> 
> Is the issue that you have a large number of sched_idle entities, and
> the occasional latency sensitive thing that wakes up for a short
> duration? Have you considered approaching this from the other
> direction (ie. if we have a latency sensitive thing wake onto a cpu
> running only sched idle stuff, we could change entity placement to
> position the latency sensitive thing further left on the timeline,
> akin to !GENTLE_FAIR_SLEEPERS).

I think this may not guarantee that latency sensitive tasks are always 
to the left of idle tasks. And it may get complicated if a 
latency-sensitive task is woken up onto a cpu which there are already 
multiple latency-sensitive tasks and sched_idle tasks.