linux-kernel - Re: [Update][PATCH v3 3/4] cpufreq: schedutil: Simplify iowait boosting

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Date:   Mon, 1 Apr 2019 12:29:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Quentin Perret <quentin.perret@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Chen Yu <yu.c.chen@...el.com>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>
Subject: Re: [Update][PATCH v3 3/4] cpufreq: schedutil: Simplify iowait
 boosting

On Mon, Apr 01, 2019 at 11:27:25AM +0200, Rafael J. Wysocki wrote:
> On Thursday, March 28, 2019 11:33:21 AM CEST Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > There is not reason for the minimum iowait boost value in the
> > schedutil cpufreq governor to depend on the available range of CPU
> > frequencies.  In fact, that dependency is generally confusing,
> > because it causes the iowait boost to behave somewhat differently
> > on CPUs with the same maximum frequency and different minimum
> > frequencies, for example.
> > 
> > For this reason, replace the min field in struct sugov_cpu
> > with a constant and choose its values to be 1/8 of
> > SCHED_CAPACITY_SCALE (for consistency with the intel_pstate
> > driver's internal governor).
> > 
> > [Note that policy->cpuinfo.max_freq will not be a constant any more
> >  after a subsequent change, so this change is depended on by it.]
> > 
> > Link: https://lore.kernel.org/lkml/20190305083202.GU32494@hirez.programming.kicks-ass.net/T/#ee20bdc98b7d89f6110c0d00e5c3ee8c2ced93c3d
> > Suggested-by: Peter Zijlstra <peterz@...radead.org>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> Any more comments on this patch?

I obviously like it :-)

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

> If not, I'll queue it up along with the rest of the series.

Thanks!