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 <20231223053634.942784-1-wudaemon@163.com>
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From: Yafang Shao <laoar.shao@gmail.com>
Date: Sun, 24 Dec 2023 19:38:25 +0800
Message-ID: <CALOAHbBdisp6opG5b0kt8skh9g5OKwXANTV2_0SLS54AMK-b1Q@mail.gmail.com>
Subject: Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error
 in sched_stat_wait trace_point
To: Junwen Wu <wudaemon@163.com>
Cc: bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com, 
	juri.lelli@redhat.com, linux-kernel@vger.kernel.org, mgorman@suse.de, 
	mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, 
	vincent.guittot@linaro.org, vschneid@redhat.com
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On Sat, Dec 23, 2023 at 1:38=E2=80=AFPM Junwen Wu <wudaemon@163.com> wrote:
>
> >It seems DL has the same issue. Pls. also fix it in update_stats_dequeue=
_dl().
> >And add the Fixes tag in the commit log:
> >Fixes: 57a5c2dafca8 ("sched/rt: Support schedstats for RT sched class")
> >Fixes: b5eb4a5f6521 ("sched/dl: Support schedstats for deadline sched cl=
ass")
>
> ok, the PATCH v3 below is ok?
>
> Subject: [PATCH v3] sched/stats: Fix rt/dl task's sched latency statistic=
s
>  error in sched_stat_wait trace_point
>
> When enable sched_stat_wait trace_point, some rt tasks sched latency so l=
ong, like this,
> sched_stat_wait: comm=3Drcu_preempt pid=3D14 delay=3D4936139545261 [ns]
> Rt task has low latency, it must have a bug. When rt task balance off sou=
rce cpu,
> dequeue operation not update the sched_statistics, so follow update_stats=
_wait_end_fair
> update method, so do dl tasks.
>
> Fixes: 57a5c2dafca8 ("sched/rt: Support schedstats for RT sched class")
> Fixes: b5eb4a5f6521 ("sched/dl: Support schedstats for deadline sched cla=
ss")
> Signed-off-by: Junwen Wu <wudaemon@163.com>

Acked-by: Yafang Shao <laoar.shao@gmail.com>

> ---
>  kernel/sched/deadline.c | 8 +++++++-
>  kernel/sched/rt.c       | 7 +++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index b28114478b82..29223163ee22 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1558,10 +1558,16 @@ update_stats_dequeue_dl(struct dl_rq *dl_rq, stru=
ct sched_dl_entity *dl_se,
>                         int flags)
>  {
>         struct task_struct *p =3D dl_task_of(dl_se);
> +       struct rq *rq =3D rq_of_dl_rq(dl_rq);
>
>         if (!schedstat_enabled())
>                 return;
> -
> +       /*
> +        * Mark the end of the wait period
> +        * if dequeueing a waiting task.
> +        */
> +       if (p && (p !=3D rq->curr))
> +                update_stats_wait_end_dl(dl_rq, dl_se);
>         if ((flags & DEQUEUE_SLEEP)) {
>                 unsigned int state;
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 6aaf0a3d6081..6a2600213991 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1360,12 +1360,19 @@ update_stats_dequeue_rt(struct rt_rq *rt_rq, stru=
ct sched_rt_entity *rt_se,
>                         int flags)
>  {
>         struct task_struct *p =3D NULL;
> +       struct rq *rq =3D rq_of_rt_se(rt_se);
>
>         if (!schedstat_enabled())
>                 return;
>
>         if (rt_entity_is_task(rt_se))
>                 p =3D rt_task_of(rt_se);
> +        /*
> +         * Mark the end of the wait period
> +         * if dequeueing a waiting task.
> +         */
> +       if (p && (p !=3D rq->curr))
> +               update_stats_wait_end_rt(rt_rq, rt_se);
>
>         if ((flags & DEQUEUE_SLEEP) && p) {
>                 unsigned int state;
>
> --
> Best regards
>


--=20
Regards
Yafang