Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler utilization data

Peter Zijlstra
2016-03-03T15:38:28Z

On Thu, Mar 03, 2016 at 03:01:15PM +0100, Vincent Guittot wrote:
> > In case a more formal derivation of this formula is needed, it is
> > based on the following 3 assumptions:
> >
> > (1) Performance is a linear function of frequency.
> > (2) Required performance is a linear function of the utilization ratio
> > x = util/max as provided by the scheduler (0 <= x <= 1).
>
> Just to mention that the utilization that you are using, varies with
> the frequency which add another variable in your equation

Right, x86 hasn't implemented arch_scale_freq_capacity(), so the
utilization values we use are all over the map. If we lower freq, the
util will go up, which would result in us bumping the freq again, etc..