linux-kernel - Re: [RFC PATCH 3/9] sched: add sched feature to disable idle core search

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Message-ID: <87mufj2gju.fsf@arm.com>
Date:   Thu, 05 Sep 2019 11:17:25 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     subhra mazumdar <subhra.mazumdar@...cle.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, tglx@...utronix.de, steven.sistare@...cle.com,
        dhaval.giani@...cle.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, viresh.kumar@...aro.org,
        tim.c.chen@...ux.intel.com, mgorman@...hsingularity.net,
        parth@...ux.ibm.com
Subject: Re: [RFC PATCH 3/9] sched: add sched feature to disable idle core search


On Fri, Aug 30, 2019 at 18:49:38 +0100, subhra mazumdar wrote...

> Add a new sched feature SIS_CORE to have an option to disable idle core
> search (select_idle_core).
>
> Signed-off-by: subhra mazumdar <subhra.mazumdar@...cle.com>
> ---
>  kernel/sched/features.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index 858589b..de4d506 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -57,6 +57,7 @@ SCHED_FEAT(TTWU_QUEUE, true)
>   */
>  SCHED_FEAT(SIS_AVG_CPU, false)
>  SCHED_FEAT(SIS_PROP, true)
> +SCHED_FEAT(SIS_CORE, true)

Why do we need a sched_feature? If you think there are systems in
which the usage of latency-nice does not make sense for in "Select Idle
Sibling", then we should probably better add a new Kconfig option.

If that's the case, you can probably use the init/Kconfig's
"Scheduler features" section, recently added by:

  commit 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting")

>  /*
>   * Issue a WARN when we do multiple update_rq_clock() calls

Best,
Patrick

-- 
#include <best/regards.h>

Patrick Bellasi