Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue

Peter Zijlstra
2024-04-29T12:14:41Z

On Sun, Apr 28, 2024 at 06:32:49PM +0200, Mike Galbraith wrote:
> On Sat, 2024-04-27 at 08:42 +0200, Mike Galbraith wrote:
> > On Fri, 2024-04-26 at 18:03 +0200, Mike Galbraith wrote:
> > > fwiw, tbench liked the previous version better.
> >
> > The culprit lies somewhere in the new PREEMPT_SHORT patch.
>
> <squint>
>
> Ah, moving the curr eligibility check into pick_curr() left an
> ineligible curr to be seen/used further down in pick_eevdf().
>
> found:
> if (!best || (curr && entity_before(curr, best)))
> best = curr;

Hmm yes, over aggressive cleanup that. Let me try again.

> Nit: PREEMPT_SHORT depending on RUN_TO_PARITY looks odd.

The thinking was that without RUN_TO_PARITY we'll always do a full pick
and it will always pick a (new) shorter deadline task over current.

The PREEMPRT_SHORT thing really is an exception to avoid RUN_TO_PARITY
from ruining latency game for short tasks.