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From:   Josh Don <joshdon@google.com>
Date:   Mon, 14 Mar 2022 17:30:35 -0700
Message-ID: <CABk29NsBEZ63eQ-avDBHe1LYj+wJNSTkCxPDQ=eTNS9_i9e0NA@mail.gmail.com>
Subject: Re: [External] Re: Subject: [PATCH] sched/fair: prioritize normal
 task over sched_idle task with vruntime offset
To:     chenying <chenying.kernel@bytedance.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Benjamin Segall <bsegall@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        duanxiongchun@bytedance.com, zhouchengming@bytedance.com,
        songmuchun@bytedance.com, zhengqi.arch@bytedance.com,
        zhoufeng.zf@bytedance.com, ligang.bdlg@bytedance.com
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On Sun, Mar 13, 2022 at 3:07 AM chenying <chenying.kernel@bytedance.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).