Re: [PATCH v7 02/14] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling

Vincent Guittot
2018-09-12T14:56:31Z

Hi Quentin,

On Wed, 12 Sep 2018 at 11:13, Quentin Perret <quentin.perret@arm.com> wrote:
>
> Schedutil requests frequency by aggregating utilization signals from
> the scheduler (CFS, RT, DL, IRQ) and applying and 25% margin on top of

quite a minor thing but s/and 25%/a 25%/

> them. Since Energy Aware Scheduling (EAS) needs to be able to predict
> the frequency requests, it needs to forecast the decisions made by the
> governor.
>
> In order to prepare the introduction of EAS, introduce
> schedutil_freq_util() to centralize the aforementioned signal
> aggregation and make it available to both schedutil and EAS. Since
> frequency selection and energy estimation still need to deal with RT and
> DL signals slightly differently, schedutil_freq_util() is called with a
> different 'type' parameter in those two contexts, and returns an
> aggregated utilization signal accordingly. While at it, introduce the
> map_util_freq() function which is designed to make schedutil's 25%
> margin usable easily for both sugov and EAS.
>
> As EAS will be able to predict schedutil's frequency requests more
> accurately than any other governor by design, it'd be sensible to make
> sure EAS cannot be used without schedutil. This will be done later, once
> EAS has actually been introduced.
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Quentin Perret <quentin.perret@arm.com>