Re: [PATCH 1/3] sched/fair: Prepare variables for increased precision of EAS estimated energy

[Vincent Guittot]

On Wed, 7 Jul 2021 at 12:41, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
>
>
>
> On 7/7/21 11:32 AM, Vincent Guittot wrote:
> > On Wed, 7 Jul 2021 at 12:29, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> >>
> >>
> >>
> >> On 7/7/21 11:11 AM, Vincent Guittot wrote:
> >>> On Wed, 7 Jul 2021 at 12:06, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> >>>>
> >>
> >> [snip]
> >>
> >>>> No. It's in 0.1uW scale, so 800Watts. Which is 16 CPUs * 64Watts
> >>>
> >>> Oh! you want 0.1uW precision .... This doesn't seem realistic at all.
> >>> I'm not even sure that the power model can even reach an accuracy of
> >>> 1mW
> >>>
> >>
> >> True, the EM is registering platform with 1mW precision, but 1uW
> >
> > Do you mean 1uW or 0.1uW ?
>
> In this patch set I've proposed 0.1uW, but I'm open to drop one
> order of magnitude. The 1uW still be good.

I don't want to underestimate the capabilities of the power model but
I don't see which benefit you will get with 0.1uW precision
With a 1uW precision the long type currently used for the returned
value is fine for 32bits machine AFAICT