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Message-ID: <CALOAHbBCpeMaCFWv7xf6YF3Endb4XTJDrXUSqjMMC3drNVdj-Q@mail.gmail.com>
Date: Sat, 21 Nov 2020 12:36:38 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: jun qian <qianjun.kernel@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Benjamin Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...e.de>, bristot@...hat.com,
LKML <linux-kernel@...r.kernel.org>,
linux-rt-users@...r.kernel.org
Subject: Re: [RFC PATCH 4/4] sched, rt: support schedstat for RT sched class
On Fri, Nov 20, 2020 at 10:39 AM jun qian <qianjun.kernel@...il.com> wrote:
>
> Yafang Shao <laoar.shao@...il.com> 于2020年11月19日周四 上午11:55写道：
> >
> > We want to measure the latency of RT tasks in our production
> > environment with schedstat facility, but currently schedstat is only
> > supported for fair sched class. This patch enable it for RT sched class
> > as well.
> >
> > The schedstat statistics are define in struct sched_entity, which is a
> > member of struct task_struct, so we can resue it for RT sched class.
> >
> > The schedstat usage in RT sched class is similar with fair sched class,
> > for example,
> > fair RT
> > enqueue update_stats_enqueue_fair update_stats_enqueue_rt
> > dequeue update_stats_dequeue_fair update_stats_dequeue_rt
> > put_prev_task update_stats_wait_start update_stats_wait_start
> > set_next_task update_stats_wait_end update_stats_wait_end
> > show /proc/[pid]/sched /proc/[pid]/sched
> >
> > The sched:sched_stats_* tracepoints can be used to trace RT tasks as
> > well.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> > ---
> > kernel/sched/rt.c | 61 ++++++++++++++++++++++++++++++++++++++++++++
> > kernel/sched/sched.h | 2 ++
> > 2 files changed, 63 insertions(+)
> >
> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> > index b9ec886702a1..a318236b7166 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -1246,6 +1246,46 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
> > dec_rt_group(rt_se, rt_rq);
> > }
> >
>
> Does the deadline schedule class should be considered also?
>
deadline sched class can be supported as well per my understanding, I
think we can do it later.
This patchset only aims to support RT sched class.
> thanks
>
> > +static inline void
> > +update_stats_enqueue_rt(struct rq *rq, struct sched_entity *se,
> > + struct sched_rt_entity *rt_se, int flags)
> > +{
> > + struct rt_rq *rt_rq = &rq->rt;
> > +
> > + if (!schedstat_enabled())
> > + return;
> > +
> > + if (rt_se != rt_rq->curr)
> > + update_stats_wait_start(rq, se);
> > +
> > + if (flags & ENQUEUE_WAKEUP)
> > + update_stats_enqueue_sleeper(rq, se);
> > +}
> > +
> > +static inline void
> > +update_stats_dequeue_rt(struct rq *rq, struct sched_entity *se,
> > + struct sched_rt_entity *rt_se, int flags)
> > +{
> > + struct rt_rq *rt_rq = &rq->rt;
> > +
> > + if (!schedstat_enabled())
> > + return;
> > +
> > + if (rt_se != rt_rq->curr)
> > + update_stats_wait_end(rq, se);
> > +
> > + if ((flags & DEQUEUE_SLEEP) && rt_entity_is_task(rt_se)) {
> > + struct task_struct *tsk = rt_task_of(rt_se);
> > +
> > + if (tsk->state & TASK_INTERRUPTIBLE)
> > + __schedstat_set(se->statistics.sleep_start,
> > + rq_clock(rq));
> > + if (tsk->state & TASK_UNINTERRUPTIBLE)
> > + __schedstat_set(se->statistics.block_start,
> > + rq_clock(rq));
> > + }
> > +}
> > +
> > /*
> > * Change rt_se->run_list location unless SAVE && !MOVE
> > *
> > @@ -1275,6 +1315,7 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
> > struct rt_prio_array *array = &rt_rq->active;
> > struct rt_rq *group_rq = group_rt_rq(rt_se);
> > struct list_head *queue = array->queue + rt_se_prio(rt_se);
> > + struct task_struct *task = rt_task_of(rt_se);
> >
> > /*
> > * Don't enqueue the group if its throttled, or when empty.
> > @@ -1288,6 +1329,8 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
> > return;
> > }
> >
> > + update_stats_enqueue_rt(rq_of_rt_rq(rt_rq), &task->se, rt_se, flags);
> > +
> > if (move_entity(flags)) {
> > WARN_ON_ONCE(rt_se->on_list);
> > if (flags & ENQUEUE_HEAD)
> > @@ -1307,7 +1350,9 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
> > {
> > struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
> > struct rt_prio_array *array = &rt_rq->active;
> > + struct task_struct *task = rt_task_of(rt_se);
> >
> > + update_stats_dequeue_rt(rq_of_rt_rq(rt_rq), &task->se, rt_se, flags);
> > if (move_entity(flags)) {
> > WARN_ON_ONCE(!rt_se->on_list);
> > __delist_rt_entity(rt_se, array);
> > @@ -1374,6 +1419,7 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
> > if (flags & ENQUEUE_WAKEUP)
> > rt_se->timeout = 0;
> >
> > + check_schedstat_required();
> > enqueue_rt_entity(rt_se, flags);
> >
> > if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
> > @@ -1574,6 +1620,12 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag
> >
> > static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first)
> > {
> > + struct sched_rt_entity *rt_se = &p->rt;
> > + struct rt_rq *rt_rq = &rq->rt;
> > +
> > + if (on_rt_rq(&p->rt))
> > + update_stats_wait_end(rq, &p->se);
> > +
> > update_stats_curr_start(rq, &p->se);
> >
> > /* The running task is never eligible for pushing */
> > @@ -1591,6 +1643,8 @@ static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool f
> > update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
> >
> > rt_queue_push_tasks(rq);
> > +
> > + rt_rq->curr = rt_se;
> > }
> >
> > static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
> > @@ -1638,6 +1692,11 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
> >
> > static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
> > {
> > + struct rt_rq *rt_rq = &rq->rt;
> > +
> > + if (on_rt_rq(&p->rt))
> > + update_stats_wait_start(rq, &p->se);
> > +
> > update_curr_rt(rq);
> >
> > update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
> > @@ -1648,6 +1707,8 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
> > */
> > if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
> > enqueue_pushable_task(rq, p);
> > +
> > + rt_rq->curr = NULL;
> > }
> >
> > #ifdef CONFIG_SMP
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index 28986736ced9..7787afbd5723 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -649,6 +649,8 @@ struct rt_rq {
> > struct rq *rq;
> > struct task_group *tg;
> > #endif
> > +
> > + struct sched_rt_entity *curr;
> > };
> >
> > static inline bool rt_rq_is_runnable(struct rt_rq *rt_rq)
> > --
> > 2.18.4
> >
--
Thanks
Yafang
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