Re: [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics

2020-10-15 Thread Peter Zijlstra 
On Thu, Oct 15, 2020 at 02:48:46PM +0800, qianjun.ker...@gmail.com wrote:
> From: jun qian 
> 
> When the sched_schedstat changes from 0 to 1, some sched se maybe
> already in the runqueue, the se->statistics.wait_start will be 0.
> So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
> wrong. We need to avoid this scenario.
> 
> Signed-off-by: jun qian 
> Reviewed-by: Yafang Shao 

Thanks!

[PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics

2020-10-14 Thread qianjun . kernel 
From: jun qian 

When the sched_schedstat changes from 0 to 1, some sched se maybe
already in the runqueue, the se->statistics.wait_start will be 0.
So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
wrong. We need to avoid this scenario.

Signed-off-by: jun qian 
Reviewed-by: Yafang Shao 
---
 kernel/sched/fair.c | 9 +
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a05..6f8ca0c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -906,6 +906,15 @@ static void update_curr_fair(struct rq *rq)
if (!schedstat_enabled())
return;
 
+   /*
+* When the sched_schedstat changes from 0 to 1, some sched se
+* maybe already in the runqueue, the se->statistics.wait_start
+* will be 0.So it will let the delta wrong. We need to avoid this
+* scenario.
+*/
+   if (unlikely(!schedstat_val(se->statistics.wait_start)))
+   return;
+
delta = rq_clock(rq_of(cfs_rq)) - 
schedstat_val(se->statistics.wait_start);
 
if (entity_is_task(se)) {
-- 
1.8.3.1

Re: [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics

2020-10-14 Thread Yafang Shao 
On Wed, Oct 14, 2020 at 9:19 PM Peter Zijlstra  wrote:
>
> On Fri, Oct 09, 2020 at 05:25:30PM +0800, qianjun.ker...@gmail.com wrote:
> > From: jun qian 
> >
> > When the sched_schedstat changes from 0 to 1, some sched se maybe
> > already in the runqueue, the se->statistics.wait_start will be 0.
> > So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
> > wrong. We need to avoid this scenario.
> >
> > Signed-off-by: jun qian 
> > Signed-off-by: Yafang Shao 
>
> This SoB chain isn't valid. Did Yafang's tag need to a reviewed-by or
> something?
>

This patch improves the behavior when sched_schedstat is changed from
0 to 1, so it looks good to me.

Reviewed-by: Yafang Shao 

> > ---
> >  kernel/sched/fair.c | 9 +
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 1a68a05..6f8ca0c 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -906,6 +906,15 @@ static void update_curr_fair(struct rq *rq)
> >   if (!schedstat_enabled())
> >   return;
> >
> > + /*
> > +  * When the sched_schedstat changes from 0 to 1, some sched se
> > +  * maybe already in the runqueue, the se->statistics.wait_start
> > +  * will be 0.So it will let the delta wrong. We need to avoid this
> > +  * scenario.
> > +  */
> > + if (unlikely(!schedstat_val(se->statistics.wait_start)))
> > + return;
> > +
> >   delta = rq_clock(rq_of(cfs_rq)) - 
> > schedstat_val(se->statistics.wait_start);
> >
> >   if (entity_is_task(se)) {
> > --
> > 1.8.3.1
> >



-- 
Thanks
Yafang

Re: [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics

2020-10-14 Thread Peter Zijlstra 
On Fri, Oct 09, 2020 at 05:25:30PM +0800, qianjun.ker...@gmail.com wrote:
> From: jun qian 
> 
> When the sched_schedstat changes from 0 to 1, some sched se maybe
> already in the runqueue, the se->statistics.wait_start will be 0.
> So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
> wrong. We need to avoid this scenario.
> 
> Signed-off-by: jun qian 
> Signed-off-by: Yafang Shao 

This SoB chain isn't valid. Did Yafang's tag need to a reviewed-by or
something?

> ---
>  kernel/sched/fair.c | 9 +
>  1 file changed, 9 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1a68a05..6f8ca0c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -906,6 +906,15 @@ static void update_curr_fair(struct rq *rq)
>   if (!schedstat_enabled())
>   return;
>  
> + /*
> +  * When the sched_schedstat changes from 0 to 1, some sched se
> +  * maybe already in the runqueue, the se->statistics.wait_start
> +  * will be 0.So it will let the delta wrong. We need to avoid this
> +  * scenario.
> +  */
> + if (unlikely(!schedstat_val(se->statistics.wait_start)))
> + return;
> +
>   delta = rq_clock(rq_of(cfs_rq)) - 
> schedstat_val(se->statistics.wait_start);
>  
>   if (entity_is_task(se)) {
> -- 
> 1.8.3.1
>

[PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics

2020-10-09 Thread qianjun . kernel 
From: jun qian 

When the sched_schedstat changes from 0 to 1, some sched se maybe
already in the runqueue, the se->statistics.wait_start will be 0.
So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
wrong. We need to avoid this scenario.

Signed-off-by: jun qian 
Signed-off-by: Yafang Shao 
---
 kernel/sched/fair.c | 9 +
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a05..6f8ca0c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -906,6 +906,15 @@ static void update_curr_fair(struct rq *rq)
if (!schedstat_enabled())
return;
 
+   /*
+* When the sched_schedstat changes from 0 to 1, some sched se
+* maybe already in the runqueue, the se->statistics.wait_start
+* will be 0.So it will let the delta wrong. We need to avoid this
+* scenario.
+*/
+   if (unlikely(!schedstat_val(se->statistics.wait_start)))
+   return;
+
delta = rq_clock(rq_of(cfs_rq)) - 
schedstat_val(se->statistics.wait_start);
 
if (entity_is_task(se)) {
-- 
1.8.3.1