linux-kernel - Re: [PATCH V5 1/3] cpuidle: play_idle: Make play

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Message-ID: <2aadcd27-b32d-89f1-8bb8-76893f007c66@linaro.org>
Date:   Tue, 29 Oct 2019 09:32:57 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 1/3] cpuidle: play_idle: Make play_idle more flexible

Hi Ulf,


On 28/10/2019 23:26, Ulf Hansson wrote:
> On Mon, 28 Oct 2019 at 15:34, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>>
>> The play_idle function has two users, the intel powerclamp and the
>> idle_injection.
>>
>> The idle injection cooling device uses the function via the
>> idle_injection powercap's APIs. Unfortunately, play_idle is currently
>> limited by the idle state depth: by default the deepest idle state is
>> selected. On the ARM[64] platforms, most of the time it is the cluster
>> idle state, the exit latency and the residency can be very high. That
>> reduces the scope of the idle injection usage because the impact on
>> the performances can be very significant.
>>
>> If the idle injection cycles can be done with a shallow state like a
>> retention state, the cooling effect would eventually give similar
>> results than the cpufreq cooling device.
>>
>> In order to prepare the function to receive an idle state parameter,
>> let's replace the 'use_deepest_state' boolean field with 'use_state'
>> and use this value to enter the specific idle state.
>>
>> The current code keeps the default behavior which is go to the deepest
>> idle state.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> Acked-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> 
> This looks good to me! Just a minor nitpick, see more below. If you
> don't like my suggestions, I am fine as is. Therefore:

Thank you very much for reviewing the patches.

I don't have any objection about renaming the variables as you suggest.

Rafael, is it fine the renaming?

> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>


[ ... ]


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