linux-kernel - Re: [PATCH] sched/fair: Use recent_used_cpu to test p->cpus

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Date:   Tue, 20 Jun 2023 13:49:09 -0400
From:   Phil Auld <pauld@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: Use recent_used_cpu to test p->cpus_ptr

On Tue, Jun 20, 2023 at 04:07:47PM +0800 Miaohe Lin wrote:
> When checking whether a recently used CPU can be a potential idle
> candidate, recent_used_cpu should be used to test p->cpus_ptr as
> p->recent_used_cpu is not equal to recent_used_cpu and candidate
> decision is made based on recent_used_cpu here.
> 
> Fixes: 89aafd67f28c ("sched/fair: Use prev instead of new target as recent_used_cpu")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 7666dbc2b788..3cc06cfca350 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7156,7 +7156,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
>  	    recent_used_cpu != target &&
>  	    cpus_share_cache(recent_used_cpu, target) &&
>  	    (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
> -	    cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
> +	    cpumask_test_cpu(recent_used_cpu, p->cpus_ptr) &&
>  	    asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) {
>  		return recent_used_cpu;
>  	}
> -- 
> 2.27.0
> 

This looks correct to me.

Reviewed-by: Phil Auld <pauld@...hat.com>


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