Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <1648789811-3788971-1-git-send-email-liuhailong@linux.alibaba.com>
In-Reply-To: <1648789811-3788971-1-git-send-email-liuhailong@linux.alibaba.com>
From:   Suren Baghdasaryan <surenb@google.com>
Date:   Fri, 1 Apr 2022 09:19:17 -0700
Message-ID: <CAJuCfpH3mzLi4bhaLUYLDDXA6uVM5Pn67aXyPefseEsAYDatSA@mail.gmail.com>
Subject: Re: [PATCH] psi: Fix trigger being fired unexpectedly at initial
To:     Hailong Liu <liuhailong@linux.alibaba.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        aniel Bristot de Oliveira <bristot@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, Mar 31, 2022 at 10:10 PM Hailong Liu
<liuhailong@linux.alibaba.com> wrote:
>
> When a trigger being created, its win.start_value and win.start_time are
> reset to zero. If group->total[PSI_POLL][t->state] has accumulated before,
> this trigger will be fired unexpectedly in the next period, even if its
> growth time does not reach its threshold.
>
> So set the window of the new trigger to the current state value.

Makes sense to me. Thanks!

>
> Signed-off-by: Hailong Liu <liuhailong@linux.alibaba.com>

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

> ---
>  kernel/sched/psi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index a4fa3aadfcba..5a49a8c8783e 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1117,7 +1117,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
>         t->state = state;
>         t->threshold = threshold_us * NSEC_PER_USEC;
>         t->win.size = window_us * NSEC_PER_USEC;
> -       window_reset(&t->win, 0, 0, 0);
> +       window_reset(&t->win, sched_clock(),
> +                       group->total[PSI_POLL][t->state], 0);
>
>         t->event = 0;
>         t->last_event_time = 0;
> --
> 2.19.1.6.gb485710b
>