[PATCH v3] sched/fair: simplfy the work when reweighting entity

[PATCH v3] sched/fair: simplfy the work when reweighting entity

[Jiang Biao]

From: Jiang Biao <benbjiang@tencent.com>

The code in reweight_entity() can be simplified.

For a sched entity on the rq, the entity accounting can be replaced by
cfs_rq instantaneous load updates currently called from within the
entity accounting.

Even though an entity on the rq can't represent a task in
reweight_entity() (a task is always dequeued before calling this
function) and so the numa task accounting and the rq->cfs_tasks list
management of the entity accounting are never called, the redundant
cfs_rq->nr_running decrement/increment will be avoided.

Signed-off-by: Jiang Biao <benbjiang@tencent.com>
---
v3<-v2: Amend commit log taking Dietmar's advice. Thx.
v2<-v1: Amend the commit log

 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04fa8dbcfa4d..18a8fc7bd0de 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3086,7 +3086,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 		/* commit outstanding execution time */
 		if (cfs_rq->curr == se)
 			update_curr(cfs_rq);
-		account_entity_dequeue(cfs_rq, se);
+		update_load_sub(&cfs_rq->load, se->load.weight);
 	}
 	dequeue_load_avg(cfs_rq, se);
 
@@ -3102,7 +3102,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 
 	enqueue_load_avg(cfs_rq, se);
 	if (se->on_rq)
-		account_entity_enqueue(cfs_rq, se);
+		update_load_add(&cfs_rq->load, se->load.weight);
 
 }
 
-- 
2.21.0

Re: [PATCH v3] sched/fair: simplfy the work when reweighting entity

[Dietmar Eggemann]

On 11/08/2020 13:32, Jiang Biao wrote:
> From: Jiang Biao <benbjiang@tencent.com>
> 
> The code in reweight_entity() can be simplified.
> 
> For a sched entity on the rq, the entity accounting can be replaced by
> cfs_rq instantaneous load updates currently called from within the
> entity accounting.
> 
> Even though an entity on the rq can't represent a task in
> reweight_entity() (a task is always dequeued before calling this
> function) and so the numa task accounting and the rq->cfs_tasks list
> management of the entity accounting are never called, the redundant
> cfs_rq->nr_running decrement/increment will be avoided.
> 
> Signed-off-by: Jiang Biao <benbjiang@tencent.com>
> ---
> v3<-v2: Amend commit log taking Dietmar's advice. Thx.
> v2<-v1: Amend the commit log
> 
>  kernel/sched/fair.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 04fa8dbcfa4d..18a8fc7bd0de 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3086,7 +3086,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
>  		/* commit outstanding execution time */
>  		if (cfs_rq->curr == se)
>  			update_curr(cfs_rq);
> -		account_entity_dequeue(cfs_rq, se);
> +		update_load_sub(&cfs_rq->load, se->load.weight);
>  	}
>  	dequeue_load_avg(cfs_rq, se);
>  
> @@ -3102,7 +3102,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
>  
>  	enqueue_load_avg(cfs_rq, se);
>  	if (se->on_rq)
> -		account_entity_enqueue(cfs_rq, se);
> +		update_load_add(&cfs_rq->load, se->load.weight);
>  
>  }

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

Re: [PATCH v3] sched/fair: simplfy the work when reweighting entity

[Vincent Guittot]

On Tue, 11 Aug 2020 at 13:32, Jiang Biao <benbjiang@gmail.com> wrote:
>
> From: Jiang Biao <benbjiang@tencent.com>
>
> The code in reweight_entity() can be simplified.
>
> For a sched entity on the rq, the entity accounting can be replaced by
> cfs_rq instantaneous load updates currently called from within the
> entity accounting.
>
> Even though an entity on the rq can't represent a task in
> reweight_entity() (a task is always dequeued before calling this
> function) and so the numa task accounting and the rq->cfs_tasks list
> management of the entity accounting are never called, the redundant
> cfs_rq->nr_running decrement/increment will be avoided.
>
> Signed-off-by: Jiang Biao <benbjiang@tencent.com>

Minor typo of the subject: s/simplfy/simplify/

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
> v3<-v2: Amend commit log taking Dietmar's advice. Thx.
> v2<-v1: Amend the commit log
>
>  kernel/sched/fair.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 04fa8dbcfa4d..18a8fc7bd0de 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3086,7 +3086,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
>                 /* commit outstanding execution time */
>                 if (cfs_rq->curr == se)
>                         update_curr(cfs_rq);
> -               account_entity_dequeue(cfs_rq, se);
> +               update_load_sub(&cfs_rq->load, se->load.weight);
>         }
>         dequeue_load_avg(cfs_rq, se);
>
> @@ -3102,7 +3102,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
>
>         enqueue_load_avg(cfs_rq, se);
>         if (se->on_rq)
> -               account_entity_enqueue(cfs_rq, se);
> +               update_load_add(&cfs_rq->load, se->load.weight);
>
>  }
>
> --
> 2.21.0
>

Re: [PATCH v3] sched/fair: simplfy the work when reweighting entity

[peterz]

On Tue, Aug 18, 2020 at 11:07:37AM +0200, Vincent Guittot wrote:
> On Tue, 11 Aug 2020 at 13:32, Jiang Biao <benbjiang@gmail.com> wrote:
> >
> > From: Jiang Biao <benbjiang@tencent.com>
> >
> > The code in reweight_entity() can be simplified.
> >
> > For a sched entity on the rq, the entity accounting can be replaced by
> > cfs_rq instantaneous load updates currently called from within the
> > entity accounting.
> >
> > Even though an entity on the rq can't represent a task in
> > reweight_entity() (a task is always dequeued before calling this
> > function) and so the numa task accounting and the rq->cfs_tasks list
> > management of the entity accounting are never called, the redundant
> > cfs_rq->nr_running decrement/increment will be avoided.
> >
> > Signed-off-by: Jiang Biao <benbjiang@tencent.com>
> 
> Minor typo of the subject: s/simplfy/simplify/

I've made it "Simplify" :-)

Thanks guys!

[tip: sched/core] sched/fair: Simplify the work when reweighting entity

[tip-bot2 for Jiang Biao]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     1724b95b92979a8ea8e55a4817d05b3bb7750958
Gitweb:        https://git.kernel.org/tip/1724b95b92979a8ea8e55a4817d05b3bb7750958
Author:        Jiang Biao <benbjiang@tencent.com>
AuthorDate:    Tue, 11 Aug 2020 19:32:09 +08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 26 Aug 2020 12:41:58 +02:00

sched/fair: Simplify the work when reweighting entity

The code in reweight_entity() can be simplified.

For a sched entity on the rq, the entity accounting can be replaced by
cfs_rq instantaneous load updates currently called from within the
entity accounting.

Even though an entity on the rq can't represent a task in
reweight_entity() (a task is always dequeued before calling this
function) and so the numa task accounting and the rq->cfs_tasks list
management of the entity accounting are never called, the redundant
cfs_rq->nr_running decrement/increment will be avoided.

Signed-off-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20200811113209.34057-1-benbjiang@tencent.com
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 90ebaa4..33699db 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3084,7 +3084,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 		/* commit outstanding execution time */
 		if (cfs_rq->curr == se)
 			update_curr(cfs_rq);
-		account_entity_dequeue(cfs_rq, se);
+		update_load_sub(&cfs_rq->load, se->load.weight);
 	}
 	dequeue_load_avg(cfs_rq, se);
 
@@ -3100,7 +3100,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 
 	enqueue_load_avg(cfs_rq, se);
 	if (se->on_rq)
-		account_entity_enqueue(cfs_rq, se);
+		update_load_add(&cfs_rq->load, se->load.weight);
 
 }