linux-kernel - Re: [PATCH 2/2] thermal: cpufreq_cooling: Reuse effective_cpu

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Date:   Wed, 15 Jul 2020 13:02:25 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Quentin Perret <qperret@...gle.com>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 2/2] thermal: cpufreq_cooling: Reuse effective_cpu_util()

On 14-07-20, 15:05, Rafael J. Wysocki wrote:
> On Tue, Jul 14, 2020 at 8:37 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >  static u32 get_load(struct cpufreq_cooling_device *cpufreq_cdev, int cpu,
> >                     int cpu_idx)
> >  {
> > -       u32 load;
> > -       u64 now, now_idle, delta_time, delta_idle;
> > -       struct time_in_idle *idle_time = &cpufreq_cdev->idle_time[cpu_idx];
> > -
> > -       now_idle = get_cpu_idle_time(cpu, &now, 0);
> > -       delta_idle = now_idle - idle_time->time;
> > -       delta_time = now - idle_time->timestamp;
> > +       unsigned long util = cpu_util_cfs(cpu_rq(cpu));
> > +       unsigned long max = arch_scale_cpu_capacity(cpu);
> >
> > -       if (delta_time <= delta_idle)
> > -               load = 0;
> > -       else
> > -               load = div64_u64(100 * (delta_time - delta_idle), delta_time);
> > -
> > -       idle_time->time = now_idle;
> > -       idle_time->timestamp = now;
> > -
> > -       return load;
> > +       util = effective_cpu_util(cpu, util, max, ENERGY_UTIL, NULL);
> 
> Hmm.
> 
> It doesn't look like cpufreq_cdev and cpu_idx are needed any more in
> this function, so maybe drop them from the arg list?

Right.

> And then there
> won't be anything specific to CPU cooling in this function, so maybe
> move it to sched and export it from there properly?

There isn't a lot happening in this routine right now TBH and am not
sure if it is really worth it to have a separate routine for this
(unless we can get rid of something for all the callers, like avoiding
a call to arch_scale_cpu_capacity() and then naming it
effective_cpu_load().

> Also it looks like max could be passed to it along with the CPU number
> instead of being always taken as arch_scale_cpu_capacity(cpu).

I am not sure what you are suggesting here. What will be the value of
max if not arch_scale_cpu_capacity() ?

-- 
viresh