linux-kernel - Re: [PATCH v3 4/4] sched: adjust sleeper credit for SCHED

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Message-ID: <CABk29NtWw53a8CWz4gDc1d57BwNyN1=uiGnSKbdxkGijs__1tg@mail.gmail.com>
Date:   Tue, 24 Aug 2021 10:12:14 -0700
From:   Josh Don <joshdon@...gle.com>
To:     Jiang Biao <benbjiang@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Paul Turner <pjt@...gle.com>,
        Oleg Rombakh <olegrom@...gle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Steve Sistare <steven.sistare@...cle.com>,
        Tejun Heo <tj@...nel.org>, Rik van Riel <riel@...riel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/4] sched: adjust sleeper credit for SCHED_IDLE entities

On Tue, Aug 24, 2021 at 1:16 AM Jiang Biao <benbjiang@...il.com> wrote:
>
> Hi,
>
> On Fri, 20 Aug 2021 at 09:06, Josh Don <joshdon@...gle.com> wrote:
> >
> > Give reduced sleeper credit to SCHED_IDLE entities. As a result, woken
> > SCHED_IDLE entities will take longer to preempt normal entities.
> >
> > The benefit of this change is to make it less likely that a newly woken
> > SCHED_IDLE entity will preempt a short-running normal entity before it
> > blocks.
> >
> > We still give a small sleeper credit to SCHED_IDLE entities, so that
> > idle<->idle competition retains some fairness.
> >
> > Example: With HZ=1000, spawned four threads affined to one cpu, one of
> > which was set to SCHED_IDLE. Without this patch, wakeup latency for the
> > SCHED_IDLE thread was ~1-2ms, with the patch the wakeup latency was
> > ~5ms.
> >
> > Signed-off-by: Josh Don <joshdon@...gle.com>
> Tried to push a similar patch before, but failed. :)
> https://lkml.org/lkml/2020/8/20/1773
> Please pick my Reviewed-by if you don't mind,
> Reviewed-by: Jiang Biao <benbjiang@...cent.com>

Done, thanks :)