linux-kernel - Re: [PATCH v5 2/2] sched/fair: Check a task has a fitting cpu when updating misfit

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Date: Tue, 20 Feb 2024 18:37:22 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Qais Yousef <qyousef@...alina.io>
Cc: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, linux-kernel@...r.kernel.org, 
	Pierre Gondois <Pierre.Gondois@....com>
Subject: Re: [PATCH v5 2/2] sched/fair: Check a task has a fitting cpu when
 updating misfit

On Tue, 20 Feb 2024 at 17:15, Qais Yousef <qyousef@...alina.io> wrote:
>
> On 02/20/24 15:59, Qais Yousef wrote:
>
> > I realized that I wanted to also add a new patch to not double balance_interval
> > for misfit failures. I think you indicated that seems the right thing to do?
>
> I think this should do it?

yes it should do it

>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 70ffbb1aa15c..b12b7de495d0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -11552,8 +11552,13 @@ static int load_balance(int this_cpu, struct rq *this_rq,
>          * repeatedly reach this code, which would lead to balance_interval
>          * skyrocketing in a short amount of time. Skip the balance_interval
>          * increase logic to avoid that.
> +        *
> +        * Similarly misfit migration which is not necessarily an indication of
> +        * the system being busy and requires lb to backoff to let it settle
> +        * down.
>          */
> -       if (env.idle == CPU_NEWLY_IDLE)
> +       if (env.idle == CPU_NEWLY_IDLE ||
> +           env.migration_type == migrate_misfit)
>                 goto out;
>
>         /* tune up the balancing interval */