Re: [RFC PATCH 4/4] sched, rt: support schedstat for RT sched class
From: jun qian
Date: Thu Nov 19 2020 - 21:39:58 EST
Yafang Shao <laoar.shao@xxxxxxxxx> 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@xxxxxxxxx>
> ---
> 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?
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
>