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

Peter Zijlstra
2016-03-10T10:30:12Z

On Thu, Mar 10, 2016 at 05:23:54PM +0700, Vincent Guittot wrote:

> > No, since its a compile time thing, we can simply do:
> >
> > #ifdef arch_scale_freq_capacity
> > next_freq = (1 + 1/n) * max_freq * (util / max)
> > #else
> > next_freq = (1 + 1/n) * current_freq * (util_raw / max)
> > #endif
>
> selecting formula at compilation is clearly better. I wrongly thought that
> it can't be accepted as a solution.

Well, its bound to get more 'interesting' since I forse implementations
not always actually doing the invariant thing.

Take for example the thing I send:

lkml.kernel.org/r/20160303162829.GB6375@twins.programming.kicks-ass.net

it both shows why you cannot talk about current_freq but also that the
above needs a little more help (for the !X86_FEATURE_APERFMPERF case).

But the !arch_scale_freq_capacity case should indeed be that simple.