linux-kernel - Re: [PATCH 1/9] sched/psi: fix periodic aggregation shut off

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Date:   Mon, 25 Jul 2022 11:34:28 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     surenb@...gle.com, mingo@...hat.com, peterz@...radead.org,
        tj@...nel.org, corbet@....net, akpm@...ux-foundation.org,
        rdunlap@...radead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, songmuchun@...edance.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH 1/9] sched/psi: fix periodic aggregation shut off

On Thu, Jul 21, 2022 at 12:04:31PM +0800, Chengming Zhou wrote:
> We don't want to wake periodic aggregation work back up if the
> task change is the aggregation worker itself going to sleep, or
> we'll ping-pong forever.
> 
> Previously, we would use psi_task_change() in psi_dequeue() when
> task going to sleep, so this check was put in psi_task_change().
> 
> But commit 4117cebf1a9f ("psi: Optimize task switch inside shared cgroups")
> defer task sleep handling to psi_task_switch(), won't go through
> psi_task_change() anymore.
> 
> So this patch move this check to psi_task_switch(). Note for defer sleep
> case, we should wake periodic avgs work for common ancestors groups,
> since those groups have next task sched_in.
> 
> Fixes: 4117cebf1a9f ("psi: Optimize task switch inside shared cgroups")
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

Good catch!

Acked-by: Johannes Weiner <hannes@...xchg.org>