linux-kernel - Re: [PATCH 2/5] cpufreq: schedutil: support scheduler cpufreq callbacks on remote CPUs

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Message-ID: <CAJZ5v0hCqGq_Q73ioVjFs-nYj60BbUOaYJ42_s_n4N+YZDgdmA@mail.gmail.com>
Date:	Fri, 20 May 2016 01:14:56 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...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>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 2/5] cpufreq: schedutil: support scheduler cpufreq
 callbacks on remote CPUs

On Fri, May 20, 2016 at 12:59 AM, Steve Muckle <steve.muckle@...aro.org> wrote:
> On Thu, May 19, 2016 at 10:55:23PM +0200, Rafael J. Wysocki wrote:
>> >> > +static inline bool sugov_queue_remote_callback(struct sugov_policy *sg_policy,
>> >> > +                                        int cpu)
>> >> > +{
>> >> > +       struct cpufreq_policy *policy = sg_policy->policy;
>> >> > +
>> >> > +       if (!cpumask_test_cpu(smp_processor_id(), policy->cpus)) {
>> >>
>> >> This check is overkill for policies that aren't shared (and we have a
>> >> special case for them already).
>> >
>> > I don't see why it is overkill -
>>
>> Because it requires more computation, memory accesses etc than simply
>> comparing smp_processor_id() with cpu.
>
> Do you have a preference on how to restructure this?

Not really.

> Otherwise I'll create a second version of sugov_update_commit, factoring out as much of
> it as I can into two inline sub-functions.

I guess in that case it might be better to fold the
sugov_update_commit() code into its callers and then factor out common
stuff into sub-functions called from there.