linux-kernel - Re: [PATCH v6 7/7][Resend] cpufreq: schedutil: New governor based on scheduler utilization data

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Message-ID: <CAJZ5v0jEueokR+bZJVRjQtmUe6BeKqUgnjWy9BZm4nGnKjT9mg@mail.gmail.com>
Date:	Wed, 30 Mar 2016 03:12:40 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Juri Lelli <juri.lelli@....com>,
	Steve Muckle <steve.muckle@...aro.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Michael Turquette <mturquette@...libre.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v6 7/7][Resend] cpufreq: schedutil: New governor based on
 scheduler utilization data

On Tue, Mar 29, 2016 at 2:58 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Monday, March 28, 2016 02:33:33 PM Viresh Kumar wrote:
>> On 22-03-16, 02:54, Rafael J. Wysocki wrote:

[cut]

>> > +static unsigned int sugov_next_freq_shared(struct sugov_policy *sg_policy,
>> > +                                      unsigned long util, unsigned long max)
>> > +{
>> > +   struct cpufreq_policy *policy = sg_policy->policy;
>> > +   unsigned int max_f = policy->cpuinfo.max_freq;
>> > +   u64 last_freq_update_time = sg_policy->last_freq_update_time;
>> > +   unsigned int j;
>> > +
>> > +   if (util == ULONG_MAX)
>> > +           return max_f;
>> > +
>> > +   for_each_cpu(j, policy->cpus) {
>> > +           struct sugov_cpu *j_sg_cpu;
>> > +           unsigned long j_util, j_max;
>> > +           u64 delta_ns;
>> > +
>> > +           if (j == smp_processor_id())
>> > +                   continue;
>>
>> Why skip local CPU completely ?
>
> Because the original util and max come from it.
>
>> And if we really want to do that, what about something like for_each_cpu_and_not
>> to kill the unnecessary if {} statement ?
>
> That will work.

Except that for_each_cpu_and_not is not defined as of today.

I guess I can play with cpumasks, but then I'm not sure that will end
up actually more efficient.