linux-kernel - Re: [PATCH 2/4] sched: cpufreq: Keep track of cpufreq utilization update flags

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Date:   Mon, 18 Dec 2017 19:30:03 -0800
From:   Joel Fernandes <joelaf@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] sched: cpufreq: Keep track of cpufreq utilization
 update flags

On Mon, Dec 18, 2017 at 7:26 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 19-12-17, 08:52, Viresh Kumar wrote:
>> On 18-12-17, 19:18, Joel Fernandes wrote:
>> > Hi Viresh,
>> >
>> > On Mon, Dec 18, 2017 at 7:12 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>> > > On 18-12-17, 12:14, Patrick Bellasi wrote:
>> > >> For example, swithing from:
>> > >>
>> > >>  - void (*func)(struct update_util_data *data, u64 time,
>> > >>  -              unsigned int flags))
>> > >>  + void (*func)(struct update_util_data *data, u64 time,
>> > >>  +              unsigned int flags, bool set))
>> > >>
>> > >> Where the additional boolean is actually used to define which
>> > >> operation we wanna perform on the flags?
>> > >
>> > > The code will eventually have the same complexity or ugliness in both
>> > > the cases. I would like to start with another flag for now and see if
>> > > people prefer another parameter.
>> >
>> > Though I think that will solve Rafael's concern of polluting the flags
>> > for something schedutil specific. I also feel adding extra callback
>> > parameter is cleaner than 2 new clear flags.
>>
>> Okay, I will then wait for Rafael to come online and comment on what
>> he would prefer before posting.
>
> I thought about it once more. If we decide eventually to add another
> parameter, then why isn't the approach that this patch takes better
> than that? i.e. Use the 31st bit of flags for clear bit ? We can
> remove setting/clearing flags for CFS, that's it.

Yes that's clean to me but then as Rafael said, the use of this flag
will be too specific for schedutil-only sg_cpu->flags clearing purpose
right?

If adding the single flag is OK in the grand cpufreq scheme of things,
then that's fine with me.

Thanks,

- Joel