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

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Message-ID: <20201021121950.GF2628@hirez.programming.kicks-ass.net>
Date:   Wed, 21 Oct 2020 14:19:50 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        kernel-janitors@...r.kernel.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,
        Valentin Schneider <valentin.schneider@....com>,
        Gilles Muller <Gilles.Muller@...ia.fr>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, viresh.kumar@...aro.org,
        srinivas.pandruvada@...ux.intel.com
Subject: Re: [PATCH] sched/fair: check for idle core

On Wed, Oct 21, 2020 at 01:56:55PM +0200, Julia Lawall wrote:
> Prior to 5.8, my machine was using intel_pstate and had few background
> tasks.  Thus the problem wasn't visible in practice.  Starting with 5.8
> the kernel decided that intel_cpufreq would be more appropriate, which
> introduced kworkers every 0.004 seconds on all cores.

That still doesn't make any sense. Are you running the legacy on-demand
thing or something?

Rafael, Srinivas, Viresh, how come it defaults to that?