linux-kernel - Re: [PATCH v2] sched/fair: check for idle core

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Message-ID: <alpine.DEB.2.22.394.2101242134530.2788@hadrien>
Date:   Sun, 24 Jan 2021 21:38:14 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Mel Gorman <mgorman@...e.de>
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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched/fair: check for idle core



On Tue, 27 Oct 2020, Mel Gorman wrote:

> On Thu, Oct 22, 2020 at 03:15:50PM +0200, Julia Lawall wrote:
> > Fixes: 11f10e5420f6 ("sched/fair: Use load instead of runnable load in wakeup path")
> > Signed-off-by: Julia Lawall <Julia.Lawall@...ia.fr>
> > Reviewed-by Vincent Guittot <vincent.guittot@...aro.org>
> >
>
> While not a universal win, it was mostly a win or neutral. In few cases
> where there was a problem, one benchmark I'm a bit suspicious of generally
> as occasionally it generates bad results for unknown and unpredictable
> reasons. In another, it was very machine specific and the differences
> were small in absolte time rather than relative time. Other tests on the
> same machine were fine so overall;
>
> Acked-by: Mel Gorman <mgorman@...e.de>

Recently, we have been testing the phoronix multicore benchmarks.  On v5.9
with this patch, the preparation time of phoronix slows down, from ~23
seconds to ~28 seconds.  In v5.11-rc4, we see 29 seconds.  It's not yet
clear what causes the problem.  But perhaps the patch should be removed
from v5.11, until the problem is understood.

commit d8fcb81f1acf651a0e50eacecca43d0524984f87

julia



>
> Thanks.
>
> --
> Mel Gorman
> SUSE Labs
>