linux-kernel - Re: [RFC][PATCH v2 2/2] cpufreq: schedutil: Avoid decreasing frequency of busy CPUs

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Message-ID: <20170321150210.GT3093@worktop>
Date:   Tue, 21 Mar 2017 16:02:10 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Joel Fernandes <joelaf@...gle.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC][PATCH v2 2/2] cpufreq: schedutil: Avoid decreasing
 frequency of busy CPUs

On Tue, Mar 21, 2017 at 03:26:06PM +0100, Rafael J. Wysocki wrote:
> +	if ((flags & SCHED_CPUFREQ_RT_DL) || this_rq()->rd->overload) {
>  		next_f = policy->cpuinfo.max_freq;

So this I think is wrong; rd->overload is set if _any_ of the CPUs in the
root domain is overloaded. And given the root domain is typically the
_entire_ machine, this would have a tendency to run at max_freq far too
often.