linux-kernel - Re: [PATCH 1/3] cpufreq: schedutil: enable fast switch earlier

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Date:   Sun, 13 Nov 2016 15:46:07 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <Juri.Lelli@....com>,
        Robin Randhawa <robin.randhawa@....com>
Subject: Re: [PATCH 1/3] cpufreq: schedutil: enable fast switch earlier

On Sat, Nov 12, 2016 at 6:19 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 12 November 2016 at 03:28, Rafael J. Wysocki <rafael@...nel.org> wrote:
>
>>> @@ -478,8 +484,6 @@ static void sugov_exit(struct cpufreq_policy *policy)
>>>         struct sugov_tunables *tunables = sg_policy->tunables;
>>>         unsigned int count;
>>>
>>> -       cpufreq_disable_fast_switch(policy);
>>> -
>>
>> ->but why is this change necessary?
>>
>> sugov_stop() has been called already, so the ordering here shouldn't matter.
>
> Because sugov_policy_free() would be using the flag fast_switch_enabled.

That's only going to happen in the next patch, though, right?  It
wouldn't hurt to write that in the changelog too.

Besides, I'm not actually sure if starting/stopping the kthread in
sugov_policy_alloc/free() is a good idea.  It sort of conflates the
allocation of memory with kthread creation.  Any chance to untangle
that?

Thanks,
Rafael