[PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point

[PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point

[Junwen Wu]

When enable sched_stat_wait trace_point, some rt tasks sched latency
so long, like this:
sched_stat_wait: comm=rcu_preempt pid=14 delay=4936139545261 [ns]
Rt task has low latency, it must have a bug. When rt task balance off
source cpu, dequeue operation not update the sched_statistics, so follow
update_stats_wait_end_fair update method.

Signed-off-by: Junwen Wu <wudaemon@163.com>
---
Changes since v1:
https://lore.kernel.org/all/20231218150322.788382-1-wudaemon@163.com/

 kernel/sched/rt.c | 7 +++++++
 1 file changed, 7 insertions(+)

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, struct sched_rt_entity *rt_se,
 			int flags)
 {
 	struct task_struct *p = NULL;
+	struct rq *rq = rq_of_rt_se(rt_se);
 
 	if (!schedstat_enabled())
 		return;
 
 	if (rt_entity_is_task(rt_se))
 		p = rt_task_of(rt_se);
+	 /*
+	  * Mark the end of the wait period
+	  * if dequeueing a waiting task.
+	  */
+	if (p && (p != rq->curr))
+		update_stats_wait_end_rt(rt_rq, rt_se);
 
 	if ((flags & DEQUEUE_SLEEP) && p) {
 		unsigned int state;
-- 
2.34.1

Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point

[Yafang Shao]

On Thu, Dec 21, 2023 at 11:03 PM Junwen Wu <wudaemon@163.com> wrote:
>
> When enable sched_stat_wait trace_point, some rt tasks sched latency
> so long, like this:
> sched_stat_wait: comm=rcu_preempt pid=14 delay=4936139545261 [ns]
> Rt task has low latency, it must have a bug. When rt task balance off
> source cpu, dequeue operation not update the sched_statistics, so follow
> update_stats_wait_end_fair update method.
>
> Signed-off-by: Junwen Wu <wudaemon@163.com>
> ---
> Changes since v1:
> https://lore.kernel.org/all/20231218150322.788382-1-wudaemon@163.com/
>
>  kernel/sched/rt.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> 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, struct sched_rt_entity *rt_se,
>                         int flags)
>  {
>         struct task_struct *p = NULL;
> +       struct rq *rq = rq_of_rt_se(rt_se);
>
>         if (!schedstat_enabled())
>                 return;
>
>         if (rt_entity_is_task(rt_se))
>                 p = rt_task_of(rt_se);
> +        /*
> +         * Mark the end of the wait period
> +         * if dequeueing a waiting task.
> +         */
> +       if (p && (p != rq->curr))
> +               update_stats_wait_end_rt(rt_rq, rt_se);

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 class")

>
>         if ((flags & DEQUEUE_SLEEP) && p) {
>                 unsigned int state;
> --
> 2.34.1
>


-- 
Regards
Yafang

Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point

[Junwen Wu]

>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 class")

ok, the PATCH v3 below is ok?

Subject: [PATCH v3] sched/stats: Fix rt/dl task's sched latency statistics
 error in sched_stat_wait trace_point

When enable sched_stat_wait trace_point, some rt tasks sched latency so long, like this,
sched_stat_wait: comm=rcu_preempt pid=14 delay=4936139545261 [ns]
Rt task has low latency, it must have a bug. When rt task balance off source 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 class")
Signed-off-by: Junwen Wu <wudaemon@163.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, struct sched_dl_entity *dl_se,
                        int flags)
 {
        struct task_struct *p = dl_task_of(dl_se);
+       struct rq *rq = 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 != 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, struct sched_rt_entity *rt_se,
                        int flags)
 {
        struct task_struct *p = NULL;
+       struct rq *rq = rq_of_rt_se(rt_se);

        if (!schedstat_enabled())
                return;

        if (rt_entity_is_task(rt_se))
                p = rt_task_of(rt_se);
+        /*
+         * Mark the end of the wait period
+         * if dequeueing a waiting task.
+         */
+       if (p && (p != rq->curr))
+               update_stats_wait_end_rt(rt_rq, rt_se);

        if ((flags & DEQUEUE_SLEEP) && p) {
                unsigned int state;

--
Best regards

Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point

[Yafang Shao]

On Sat, Dec 23, 2023 at 1:38 PM 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 class")
>
> ok, the PATCH v3 below is ok?
>
> Subject: [PATCH v3] sched/stats: Fix rt/dl task's sched latency statistics
>  error in sched_stat_wait trace_point
>
> When enable sched_stat_wait trace_point, some rt tasks sched latency so long, like this,
> sched_stat_wait: comm=rcu_preempt pid=14 delay=4936139545261 [ns]
> Rt task has low latency, it must have a bug. When rt task balance off source 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 class")
> 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, struct sched_dl_entity *dl_se,
>                         int flags)
>  {
>         struct task_struct *p = dl_task_of(dl_se);
> +       struct rq *rq = 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 != 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, struct sched_rt_entity *rt_se,
>                         int flags)
>  {
>         struct task_struct *p = NULL;
> +       struct rq *rq = rq_of_rt_se(rt_se);
>
>         if (!schedstat_enabled())
>                 return;
>
>         if (rt_entity_is_task(rt_se))
>                 p = rt_task_of(rt_se);
> +        /*
> +         * Mark the end of the wait period
> +         * if dequeueing a waiting task.
> +         */
> +       if (p && (p != rq->curr))
> +               update_stats_wait_end_rt(rt_rq, rt_se);
>
>         if ((flags & DEQUEUE_SLEEP) && p) {
>                 unsigned int state;
>
> --
> Best regards
>


-- 
Regards
Yafang