linux-kernel - Re: [PATCH] sched/stats: correct the wait

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Message-ID: <4af61dbb-ab24-4f5a-8bc7-2dce3cbdc2cb@126.com>
Date: Wed, 26 Nov 2025 10:01:24 +0800
From: Honglei Wang <jameshongleiwang@....com>
To: 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, vschneid@...hat.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/stats: correct the wait_start calculation logic

Gentle ping on this one submitted a couple of weeks earlier. Is it
worthy of being picked?

Thanks,
Honglei

On 11/13/25 8:43 PM, Honglei Wang wrote:
> It's not necessary to do the delta-related subtraction if the task
> is not on rq migrating. Add the migrating related judgment back.
> 
> Signed-off-by: Honglei Wang <jameshongleiwang@....com>
> ---
>  kernel/sched/stats.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
> index d1c9429a4ac5..60560fb31e63 100644
> --- a/kernel/sched/stats.c
> +++ b/kernel/sched/stats.c
> @@ -12,7 +12,8 @@ void __update_stats_wait_start(struct rq *rq, struct task_struct *p,
>  	wait_start = rq_clock(rq);
>  	prev_wait_start = schedstat_val(stats->wait_start);
>  
> -	if (p && likely(wait_start > prev_wait_start))
> +	if (p && task_on_rq_migrating(p) &&
> +	    likely(wait_start > prev_wait_start))
>  		wait_start -= prev_wait_start;
>  
>  	__schedstat_set(stats->wait_start, wait_start);