linux-kernel - Re: [RFCv7 PATCH 03/10] sched: scheduler-driven cpu frequency selection

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Message-ID: <20160301132647.GV6357@twins.programming.kicks-ass.net>
Date:	Tue, 1 Mar 2016 14:26:47 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Ingo Molnar <mingo@...hat.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Ricky Liang <jcliang@...omium.org>
Subject: Re: [RFCv7 PATCH 03/10] sched: scheduler-driven cpu frequency
 selection

On Fri, Feb 26, 2016 at 08:17:46PM -0800, Steve Muckle wrote:
> > But then it would only make a difference if cpufreq_update_util() was not
> > used at all (ie. no callbacks installed for any policies by anyone).  The
> > only reason why it may matter is that the total number of systems using
> > the performance governor is quite large AFAICS and they would benefit from
> > that.
> 
> I'd think that's a benefit worth preserving, but I guess that's Peter
> and Ingo's call.

Probably worth it, most of this is on rather fast paths.

See commit 1cde2930e154 ("sched/preempt: Add static_key() to
preempt_notifiers") for example.