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SubjectRe: [PATCH 2/2] thermal: cpufreq_cooling: Reuse effective_cpu_util()
On 17-07-20, 11:46, Vincent Guittot wrote:
> On Thu, 16 Jul 2020 at 16:24, Lukasz Luba <lukasz.luba@arm.com> wrote:
> > On 7/16/20 12:56 PM, Peter Zijlstra wrote:
> > > Currently cpufreq_cooling appears to estimate the CPU energy usage by
> > > calculating the percentage of idle time using the per-cpu cpustat stuff,
> > > which is pretty horrific.
> >
> > Even worse, it then *samples* the *current* CPU frequency at that
> > particular point in time and assumes that when the CPU wasn't idle
> > during that period - it had *this* frequency...
>
> So there is 2 problems in the power calculation of cpufreq cooling device :
> - How to get an accurate utilization level of the cpu which is what
> this patch is trying to fix because using idle time is just wrong
> whereas scheduler utilization is frequency invariant

Since this patch is targeted only towards fixing this particular
problem, should I change something in the patch to make it acceptable
?

> - How to get power estimate from this utilization level. And as you
> pointed out, using the current freq which is not accurate.

This should be tackled separately I believe.

--
viresh

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