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From: Alex Shi <seakeel@gmail.com>
Date: Tue, 2 Jan 2024 21:00:22 +0800
Message-ID: <CAJy-Am=R=gRFqSdGjXaMqq7Yetpp-4=bLtnP-87GepN4zff5Tg@mail.gmail.com>
Subject: Re: [PATCH] sched/tracing: correct the task blocking state
To: Valentin Schneider <vschneid@redhat.com>
Cc: alexs@kernel.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>, 
	Daniel Bristot de Oliveira <bristot@redhat.com>, linux-kernel@vger.kernel.org, curuwang@tencent.com
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On Tue, Jan 2, 2024 at 6:19=E2=80=AFPM Valentin Schneider <vschneid@redhat.=
com> wrote:
>
> On 02/01/24 15:33, alexs@kernel.org wrote:
> > From: Alex Shi <alexs@kernel.org>
> >
> > commit 80ed87c8a9ca ("sched/wait: Introduce TASK_NOLOAD and TASK_IDLE")
> > stopped the idle kthreads contribution to loadavg. Also task idle shoul=
d
> > separated from blocked state too, otherwise we will get incorrect task
> > blocking state from event tracing sched:sched_stat_blocked.
> >
>
> Why is that incorrect? AFAICT we have mapped the (schedstat) 'blocked'
> meaning to TASK_UNINTERRUPTIBLE. TASK_IDLE tasks don't contribute to
> loadavg yes, but they are still in an UNINTERRUPTIBLE wait.


Hi Valentin,
Thanks a lot for the reply.

I agree with you the current usage, but if so, we account for the idle task=
 into
blocked state. And it's better to distinguish between idle and block.

>
> > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> > index b28114478b82..b6afa596f071 100644
> > --- a/kernel/sched/deadline.c
> > +++ b/kernel/sched/deadline.c
> > @@ -1570,7 +1570,7 @@ update_stats_dequeue_dl(struct dl_rq *dl_rq, stru=
ct sched_dl_entity *dl_se,
> >                       __schedstat_set(p->stats.sleep_start,
> >                                       rq_clock(rq_of_dl_rq(dl_rq)));
> >
> > -             if (state & TASK_UNINTERRUPTIBLE)
> > +             if (is_blocked_task_state(state))
> >                       __schedstat_set(p->stats.block_start,
> >                                       rq_clock(rq_of_dl_rq(dl_rq)));
>
> This change makes it so tasks waiting in TASK_IDLE have their waiting
> ignored by schedstat (they are seen as neither INTERRUPTIBLE nor UNINTERR=
UPTIBLE).
>

Right, maybe it's time to add a new state for TASK_IDLE?

Many thanks!
Alex Shi