linux-kernel - Re: [PATCH] sched/fair: avoid vruntime compensation for SCHED

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Message-ID: <CAPJCdBk_PeWExFDu23kWMCus_Yy7nsf_kLtEu9ZBAWurHmj0wA@mail.gmail.com>
Date:   Thu, 20 Aug 2020 22:24:07 +0800
From:   Jiang Biao <benbjiang@...il.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jiang Biao <benbjiang@...cent.com>
Subject: Re: [PATCH] sched/fair: avoid vruntime compensation for SCHED_IDLE task

On Thu, 20 Aug 2020 at 22:09, Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> On Thu, 20 Aug 2020 at 15:44, <peterz@...radead.org> wrote:
> >
> > > That's been said, not compensating the vruntime for a sched_idle task
> > > makes sense for me. Even if that will only help for others task in the
> > > same cfs_rq
> >
> > Yeah, but it is worth the extra pointer chasing and branches?
>
> For that I let Jiang provides figures to show the worthful
I'll try to have some tests and show the wakeup latency difference
after applying the patch later.

Thanks for your time.
Regards
Jiang
>
> >
> > Then again, I suppose we started all that with the idle_h_nr_running
> > nonsense :/