linux-kernel - Re: [PATCH v2 1/2] x86,sched: Add support for frequency invariance

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Date:   Fri, 4 Oct 2019 13:48:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Giovanni Gherdovich <ggherdovich@...e.cz>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...e.de>,
        Len Brown <lenb@...nel.org>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Paul Turner <pjt@...gle.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Quentin Perret <qperret@...rret.net>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Doug Smythies <dsmythies@...us.net>
Subject: Re: [PATCH v2 1/2] x86,sched: Add support for frequency invariance

On Thu, Oct 03, 2019 at 07:53:49PM +0200, Rafael J. Wysocki wrote:
> On Thursday, October 3, 2019 2:15:37 PM CEST Peter Zijlstra wrote:
> > On Thu, Oct 03, 2019 at 12:27:52PM +0200, Rafael J. Wysocki wrote:
> > > > +	if (smp_processor_id() != 0)
> > > > +		return;

> Well, but the smp_processor_id() check has nothing to do with whether or not
> this is "core" or "atom" or something else, for example.

It is dodgy to begin with, it hard assumes we boot on cpu-0. A
'initialized' state would probably be better.