linux-kernel - Re: [Update][PATCH v7 7/7] cpufreq: schedutil: New governor based on scheduler utilization data

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Date:	Wed, 30 Mar 2016 10:05:55 -0700
From:	Steve Muckle <steve.muckle@...aro.org>
To:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Juri Lelli <juri.lelli@....com>,
	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: [Update][PATCH v7 7/7] cpufreq: schedutil: New governor based on
 scheduler utilization data

On 03/30/2016 04:31 AM, Rafael J. Wysocki wrote:
>>> >> +static int sugov_limits(struct cpufreq_policy *policy)
>>> >> +{
>>> >> +     struct sugov_policy *sg_policy = policy->governor_data;
>>> >> +
>>> >> +     if (!policy->fast_switch_enabled) {
>>> >> +             mutex_lock(&sg_policy->work_lock);
>>> >> +
>>> >> +             if (policy->max < policy->cur)
>>> >> +                     __cpufreq_driver_target(policy, policy->max,
>>> >> +                                             CPUFREQ_RELATION_H);
>>> >> +             else if (policy->min > policy->cur)
>>> >> +                     __cpufreq_driver_target(policy, policy->min,
>>> >> +                                             CPUFREQ_RELATION_L);
>>> >> +
>>> >> +             mutex_unlock(&sg_policy->work_lock);
>>> >> +     }
>>> >> +
>>> >> +     sg_policy->need_freq_update = true;
>> >
>> > I am wondering why we need to do this for !fast_switch_enabled case?
>
> That will cause the rate limit to be ignored in the utilization update
> handler which may be necessary if it is set to a relatively large
> value (like 1 s).

But why is that necessary for !fast_switch_enabled? In that case the
frequency has been adjusted to satisfy the new limits here, so ignoring
the rate limit shouldn't be necessary. In other words why not

} else {
	sg_policy->need_freq_update = true;
}