linux-kernel - Re: [PATCH] cpufreq: Rebuild sched-domains when removing cpufreq driver

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Message-ID: <e028af69-5583-5378-9573-71e46314687d@arm.com>
Date:   Fri, 29 Sep 2023 09:22:37 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        linux-kernel@...r.kernel.org,
        Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
        vschneid@...hat.com, "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpufreq: Rebuild sched-domains when removing cpufreq
 driver



On 9/29/23 05:27, Viresh Kumar wrote:
> On 28-09-23, 14:49, Pierre Gondois wrote:
>> Another solution would be to call sched_cpufreq_governor_change()
>> from cpufreq_schedutil's init()/exit() callbacks. This would make
>> more sense as EAS/schedutil cpufreq are tightly bound, and it would
>> allow to cover all the possible paths.
>>
>> When tried locally, it seems to cover all scenarios:
>> - insmod/rmmod a cpufreq driver
>> - changing the governor policy
>> - offlining all the CPUs of a pd
> 
> Right now it is done for all governors. We don't need that ? We just care about
> schedutil here ?
> 

Yes exact, EAS requires the schedutil governor to be used by all policies. The purpose
of this function is to re-evaluate if EAS enablement conditions are met. I.e., if one
policy changed from/to schedutil, if EAS must be [de|re]activated.