Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue
From: Vincent Guittot
Date: Mon Dec 02 2024 - 05:00:20 EST
On Mon, 2 Dec 2024 at 10:23, Luis Machado <luis.machado@xxxxxxx> wrote:
>
> On 12/2/24 09:17, Vincent Guittot wrote:
> > On Sun, 1 Dec 2024 at 14:30, Mike Galbraith <efault@xxxxxx> wrote:
> >>
> >> Greetings,
> >>
> >> On Fri, 2024-11-29 at 17:17 +0100, Vincent Guittot wrote:
> >>> Delayed dequeued feature keeps a sleeping sched_entitiy enqueued until its
> >>> lag has elapsed. As a result, it stays also visible in the statistics that
> >>> are used to balance the system and in particular the field h_nr_running.
> >>>
> >>> This serie fixes those metrics by creating a new h_nr_queued that tracks
> >>> all queued tasks. It renames h_nr_running into h_nr_runnable and restores
> >>> the behavior of h_nr_running i.e. tracking the number of fair tasks that
> >>> want to run.
> >>>
> >>> h_nr_runnable is used in several places to make decision on load balance:
> >>> - PELT runnable_avg
> >>> - deciding if a group is overloaded or has spare capacity
> >>> - numa stats
> >>> - reduced capacity management
> >>> - load balance between groups
> >>
> >> I took the series for a spin in tip v6.12-10334-gb1b238fba309, but
> >> runnable seems to have an off-by-one issue, causing it to wander ever
> >> further south.
> >>
> >> patches 1-3 applied.
> >> .h_nr_runnable : -3046
> >> .runnable_avg : 450189777126
> >
> > Yeah, I messed up something around finish_delayed_dequeue_entity().
> > I'm' going to prepare a v3>
>
> Maybe something similar to what I ran into here?
>
> https://lore.kernel.org/lkml/6df12fde-1e0d-445f-8f8a-736d11f9ee41@xxxxxxx/
I'm going to have a look
>
> >>
> >> full set applied.
> >> .h_nr_runnable : -5707
> >> .runnable_avg : 4391793519526
> >>
> >> -Mike
>