linux-kernel - Re: [PATCH RFC v4] cpufreq: schedutil: Make iowait boost more energy efficient

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Date:   Wed, 12 Jul 2017 11:36:30 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Joel Fernandes <joelaf@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Juri Lelli <juri.lelli@....com>,
        Andres Oportus <andresoportus@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH RFC v4] cpufreq: schedutil: Make iowait boost more energy
 efficient

On Wed, Jul 12, 2017 at 10:30:35AM +0530, Viresh Kumar wrote:
> On 11-07-17, 07:14, Joel Fernandes wrote:

> > Another approach than setting min in sugov_set_iowait_boost, is, since
> > we have already retrieved the current util, we can check if flags ==
> > SCHED_CPUFREQ_IOWAIT, then set initial the iowait_boost such that
> > (iowait_boost / iowait_boost_max) is aleast equal to (util / max) or
> > iowait_boost_min, which ever is lower.
> 
> So my concerns weren't only about the initial min value, but also that you
> reduce the freq from sugov_set_iowait_boost(). We can discuss what the ideal
> value to start with can be.

I'm not sure I see that. He only mucks with iowait_boost, not the actual
frequency afaict.

And sugov_iowait_boost() picks the highest of util vs iowait_boost,
which wasn't changed.

Or am I completely missing something? (that code is a bit hard to
follow)