Re: [RFC PATCH 1/1] sched/pelt: Introduce PELT multiplier

[Vincent Guittot]

On Fri, 2 Sept 2022 at 09:54, Dietmar Eggemann <dietmar.eggemann@xxxxxxx> wrote:
>
> On 29/08/2022 12:13, Vincent Guittot wrote:
> > On Mon, 29 Aug 2022 at 12:03, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >>
> >> On Mon, Aug 29, 2022 at 10:08:13AM +0200, Peter Zijlstra wrote:
> >>> On Mon, Aug 29, 2022 at 07:54:50AM +0200, Dietmar Eggemann wrote:
> >>>> From: Vincent Donnefort <vincent.donnefort@xxxxxxx>
>
> [...]
>
> >>> Hurmph... I'd almost go write you something like
> >>> static_call()/static_branch() but for immediates.
> >>>
> >>> That said; given there's only like 3 options, perhaps a few
> >>> static_branch() instances work just fine ?
> >>
> >> Also, I'm not at all sure about exposing that as an official sysctl.
> >
> > Me too, I would even make it a boot time parameter so we can remove
>
> Isn't a sched feature even less official than a boot parameter?
> But AFAIK at least some of the Android folks want to change this during
> runtime and they don't have debugfs mounted.
>
> > the new clock_task_mult clock and left shift clock_taslk or the delta
> > before passing it to clock_pelt
>
> We still need rq_clock_task_mult(rq), i.e. `rq->clock_task_mult` in
> _update_idle_rq_clock_pelt() though.

Why ? If the mult is defined at boot we just have to use
"rq_clock_task(rq) << mult" instead of rq_clock_task(rq) when updating
clock_pelt