* [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point
@ 2023-12-21 15:02 Junwen Wu
2023-12-22 8:16 ` Yafang Shao
0 siblings, 1 reply; 4+ messages in thread
From: Junwen Wu @ 2023-12-21 15:02 UTC (permalink / raw)
To: mingo, laoar.shao, peterz, juri.lelli, vincent.guittot,
dietmar.eggemann, rostedt, bsegall
Cc: mgorman, bristot, vschneid, linux-kernel, 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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point
2023-12-21 15:02 [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point Junwen Wu
@ 2023-12-22 8:16 ` Yafang Shao
2023-12-23 5:36 ` Junwen Wu
0 siblings, 1 reply; 4+ messages in thread
From: Yafang Shao @ 2023-12-22 8:16 UTC (permalink / raw)
To: Junwen Wu
Cc: mingo, peterz, juri.lelli, vincent.guittot, dietmar.eggemann,
rostedt, bsegall, mgorman, bristot, vschneid, linux-kernel
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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point
2023-12-22 8:16 ` Yafang Shao
@ 2023-12-23 5:36 ` Junwen Wu
2023-12-24 11:38 ` Yafang Shao
0 siblings, 1 reply; 4+ messages in thread
From: Junwen Wu @ 2023-12-23 5:36 UTC (permalink / raw)
To: laoar.shao
Cc: bristot, bsegall, dietmar.eggemann, juri.lelli, linux-kernel,
mgorman, mingo, peterz, rostedt, vincent.guittot, vschneid,
wudaemon
>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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point
2023-12-23 5:36 ` Junwen Wu
@ 2023-12-24 11:38 ` Yafang Shao
0 siblings, 0 replies; 4+ messages in thread
From: Yafang Shao @ 2023-12-24 11:38 UTC (permalink / raw)
To: Junwen Wu
Cc: bristot, bsegall, dietmar.eggemann, juri.lelli, linux-kernel,
mgorman, mingo, peterz, rostedt, vincent.guittot, vschneid
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
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-12-21 15:02 [PATCH v2] sched/rt: Fix rt task's sched latency statistics error in sched_stat_wait trace_point Junwen Wu
2023-12-22 8:16 ` Yafang Shao
2023-12-23 5:36 ` Junwen Wu
2023-12-24 11:38 ` Yafang Shao
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