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

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Date:   Sat, 14 Sep 2019 12:57:08 +0200
From:   Quentin Perret <qperret@...rret.net>
To:     Giovanni Gherdovich <ggherdovich@...e.cz>
Cc:     srinivas.pandruvada@...ux.intel.com, tglx@...utronix.de,
        mingo@...hat.com, peterz@...radead.org, bp@...e.de,
        lenb@...nel.org, rjw@...ysocki.net, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mgorman@...hsingularity.net, matt@...eblueprint.co.uk,
        viresh.kumar@...aro.org, juri.lelli@...hat.com, pjt@...gle.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com
Subject: Re: [PATCH 1/2] x86,sched: Add support for frequency invariance

Hi Giovanni

On Monday 09 Sep 2019 at 04:42:15 (+0200), Giovanni Gherdovich wrote:
> +static inline long arch_scale_freq_capacity(int cpu)
> +{
> +	if (static_cpu_has(X86_FEATURE_APERFMPERF))
> +		return per_cpu(arch_cpu_freq, cpu);

So, if this is conditional, perhaps you could also add this check in an
x86-specific implementation of arch_scale_freq_invariant() ? That would
guide sugov in the right path (see get_next_freq()) if APERF/MPERF are
unavailable.

> +	return 1024 /* SCHED_CAPACITY_SCALE */;
> +}

Thanks,
Quentin