diff mbox series

[v2] sched/fair: merge same code in enqueue_task_fair

Message ID 202312131510+0800-wangjinchao@xfusion.com
State New
Headers
Series [v2] sched/fair: merge same code in enqueue_task_fair |

Commit Message

Wang Jinchao Dec. 13, 2023, 7:12 a.m. UTC 
  The code below is duplicated in two for loops and need to be
   consolidated

Signed-off-by: WangJinchao <wangjinchao@xfusion.com>
---
 kernel/sched/fair.c | 31 ++++++++-----------------------
 1 file changed, 8 insertions(+), 23 deletions(-)

Comments

Abel Wu Dec. 13, 2023, 8:18 a.m. UTC | #1 
Hi Jinchao,

On 12/13/23 3:12 PM, WangJinchao Wrote:
> The code below is duplicated in two for loops and need to be
>     consolidated

It doesn't need to, but it can actually bring some benefit from
the point of view of text size, especially in warehouse-scale
computers where icache is extremely contended.

add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-56 (-56)
Function                                     old     new   delta
enqueue_task_fair                            936     880     -56
Total: Before=64899, After=64843, chg -0.09%

> 
> Signed-off-by: WangJinchao <wangjinchao@xfusion.com>
> ---
>   kernel/sched/fair.c | 31 ++++++++-----------------------
>   1 file changed, 8 insertions(+), 23 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d7a3c63a2171..e1373bfd4f2e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6681,30 +6681,15 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>   		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
>   
>   	for_each_sched_entity(se) {
> -		if (se->on_rq)
> -			break;
>   		cfs_rq = cfs_rq_of(se);
> -		enqueue_entity(cfs_rq, se, flags);
> -
> -		cfs_rq->h_nr_running++;
> -		cfs_rq->idle_h_nr_running += idle_h_nr_running;
> -
> -		if (cfs_rq_is_idle(cfs_rq))
> -			idle_h_nr_running = 1;
> -
> -		/* end evaluation on encountering a throttled cfs_rq */
> -		if (cfs_rq_throttled(cfs_rq))
> -			goto enqueue_throttle;
> -
> -		flags = ENQUEUE_WAKEUP;
> -	}
> -
> -	for_each_sched_entity(se) {
> -		cfs_rq = cfs_rq_of(se);
> -
> -		update_load_avg(cfs_rq, se, UPDATE_TG);
> -		se_update_runnable(se);
> -		update_cfs_group(se);
> +		if (se->on_rq) {
> +			update_load_avg(cfs_rq, se, UPDATE_TG);
> +			se_update_runnable(se);
> +			update_cfs_group(se);
> +		} else {
> +			enqueue_entity(cfs_rq, se, flags);
> +			flags = ENQUEUE_WAKEUP;
> +		}
>   
>   		cfs_rq->h_nr_running++;
>   		cfs_rq->idle_h_nr_running += idle_h_nr_running;

I have no strong opinon about this 'cleanup', but the same pattern
can also be found in dequeue_task_fair() and I think it would be
better get them synchronized.

Thanks,
	Abel
Vincent Guittot Dec. 13, 2023, 8:24 a.m. UTC | #2 
On Wed, 13 Dec 2023 at 09:19, Abel Wu <wuyun.abel@bytedance.com> wrote:
>
> Hi Jinchao,
>
> On 12/13/23 3:12 PM, WangJinchao Wrote:
> > The code below is duplicated in two for loops and need to be
> >     consolidated
>
> It doesn't need to, but it can actually bring some benefit from
> the point of view of text size, especially in warehouse-scale
> computers where icache is extremely contended.
>
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-56 (-56)
> Function                                     old     new   delta
> enqueue_task_fair                            936     880     -56
> Total: Before=64899, After=64843, chg -0.09%
>
> >
> > Signed-off-by: WangJinchao <wangjinchao@xfusion.com>
> > ---
> >   kernel/sched/fair.c | 31 ++++++++-----------------------
> >   1 file changed, 8 insertions(+), 23 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index d7a3c63a2171..e1373bfd4f2e 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6681,30 +6681,15 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> >               cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
> >
> >       for_each_sched_entity(se) {
> > -             if (se->on_rq)
> > -                     break;
> >               cfs_rq = cfs_rq_of(se);
> > -             enqueue_entity(cfs_rq, se, flags);
> > -
> > -             cfs_rq->h_nr_running++;
> > -             cfs_rq->idle_h_nr_running += idle_h_nr_running;
> > -
> > -             if (cfs_rq_is_idle(cfs_rq))
> > -                     idle_h_nr_running = 1;
> > -
> > -             /* end evaluation on encountering a throttled cfs_rq */
> > -             if (cfs_rq_throttled(cfs_rq))
> > -                     goto enqueue_throttle;
> > -
> > -             flags = ENQUEUE_WAKEUP;
> > -     }
> > -
> > -     for_each_sched_entity(se) {
> > -             cfs_rq = cfs_rq_of(se);
> > -
> > -             update_load_avg(cfs_rq, se, UPDATE_TG);
> > -             se_update_runnable(se);
> > -             update_cfs_group(se);
> > +             if (se->on_rq) {
> > +                     update_load_avg(cfs_rq, se, UPDATE_TG);
> > +                     se_update_runnable(se);
> > +                     update_cfs_group(se);
> > +             } else {
> > +                     enqueue_entity(cfs_rq, se, flags);
> > +                     flags = ENQUEUE_WAKEUP;
> > +             }
> >
> >               cfs_rq->h_nr_running++;
> >               cfs_rq->idle_h_nr_running += idle_h_nr_running;
>
> I have no strong opinon about this 'cleanup', but the same pattern
> can also be found in dequeue_task_fair() and I think it would be
> better get them synchronized.

I agree, I don't see any benefit from this change

>
> Thanks,
>         Abel
diff mbox series

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d7a3c63a2171..e1373bfd4f2e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6681,30 +6681,15 @@  enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
 
 	for_each_sched_entity(se) {
-		if (se->on_rq)
-			break;
 		cfs_rq = cfs_rq_of(se);
-		enqueue_entity(cfs_rq, se, flags);
-
-		cfs_rq->h_nr_running++;
-		cfs_rq->idle_h_nr_running += idle_h_nr_running;
-
-		if (cfs_rq_is_idle(cfs_rq))
-			idle_h_nr_running = 1;
-
-		/* end evaluation on encountering a throttled cfs_rq */
-		if (cfs_rq_throttled(cfs_rq))
-			goto enqueue_throttle;
-
-		flags = ENQUEUE_WAKEUP;
-	}
-
-	for_each_sched_entity(se) {
-		cfs_rq = cfs_rq_of(se);
-
-		update_load_avg(cfs_rq, se, UPDATE_TG);
-		se_update_runnable(se);
-		update_cfs_group(se);
+		if (se->on_rq) {
+			update_load_avg(cfs_rq, se, UPDATE_TG);
+			se_update_runnable(se);
+			update_cfs_group(se);
+		} else {
+			enqueue_entity(cfs_rq, se, flags);
+			flags = ENQUEUE_WAKEUP;
+		}
 
 		cfs_rq->h_nr_running++;
 		cfs_rq->idle_h_nr_running += idle_h_nr_running;