linux-kernel - Re: [PATCH v2] psi: fix possible missing or delayed pending event

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Message-ID: <CAJuCfpF592xFTKP8x-qgRVJ0y3kxJZZk3u8MGM3cBPoPVXYxWg@mail.gmail.com>
Date:   Wed, 21 Sep 2022 22:18:42 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Hao Lee <haolee.swjtu@...il.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] psi: fix possible missing or delayed pending event

On Mon, Sep 19, 2022 at 12:23 AM Hao Lee <haolee.swjtu@...il.com> wrote:
>
> When a pending event exists and growth is less than the threshold, the
> current logic is to skip this trigger without generating event. However,
> from e6df4ead85d9 ("psi: fix possible trigger missing in the window"),
> our purpose is to generate event as long as pending event exists and the
> rate meets the limit, no matter what growth is.
> This patch handles this case properly.
>
> Fixes: e6df4ead85d9 ("psi: fix possible trigger missing in the window")
> Signed-off-by: Hao Lee <haolee.swjtu@...il.com>

Acked-by: Suren Baghdasaryan <surenb@...gle.com>

Thanks!

> ---
>  kernel/sched/psi.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 9711827e3..7d305d0e0 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -539,10 +539,12 @@ static u64 update_triggers(struct psi_group *group, u64 now)
>
>                         /* Calculate growth since last update */
>                         growth = window_update(&t->win, now, total[t->state]);
> -                       if (growth < t->threshold)
> -                               continue;
> +                       if (!t->pending_event) {
> +                               if (growth < t->threshold)
> +                                       continue;
>
> -                       t->pending_event = true;
> +                               t->pending_event = true;
> +                       }
>                 }
>                 /* Limit event signaling to once per window */
>                 if (now < t->last_event_time + t->win.size)
> --
> 2.21.0
>