[v2] Simplify Util_est

[PATCH v2 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)

Posted by Vincent Guittot 2 years ago

sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature
in order to check for possibly related regressions. After 3 years, it has
never been used and no regression has been reported. Let remove it
and make fast increase a permanent behavior.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-and-tested-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
Reviewed-by: Tang Yizhou <yizhou.tang@shopee.com>
---
 Documentation/scheduler/schedutil.rst                    | 7 +++----
 Documentation/translations/zh_CN/scheduler/schedutil.rst | 7 +++----
 kernel/sched/fair.c                                      | 8 +++-----
 kernel/sched/features.h                                  | 1 -
 4 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/Documentation/scheduler/schedutil.rst b/Documentation/scheduler/schedutil.rst
index 32c7d69fc86c..803fba8fc714 100644
--- a/Documentation/scheduler/schedutil.rst
+++ b/Documentation/scheduler/schedutil.rst
@@ -90,8 +90,8 @@ For more detail see:
  - Documentation/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
 
 
-UTIL_EST / UTIL_EST_FASTUP
-==========================
+UTIL_EST
+========
 
 Because periodic tasks have their averages decayed while they sleep, even
 though when running their expected utilization will be the same, they suffer a
@@ -99,8 +99,7 @@ though when running their expected utilization will be the same, they suffer a
 
 To alleviate this (a default enabled option) UTIL_EST drives an Infinite
 Impulse Response (IIR) EWMA with the 'running' value on dequeue -- when it is
-highest. A further default enabled option UTIL_EST_FASTUP modifies the IIR
-filter to instantly increase and only decay on decrease.
+highest. UTIL_EST filters to instantly increase and only decay on decrease.
 
 A further runqueue wide sum (of runnable tasks) is maintained of:
 
diff --git a/Documentation/translations/zh_CN/scheduler/schedutil.rst b/Documentation/translations/zh_CN/scheduler/schedutil.rst
index d1ea68007520..7c8d87f21c42 100644
--- a/Documentation/translations/zh_CN/scheduler/schedutil.rst
+++ b/Documentation/translations/zh_CN/scheduler/schedutil.rst
@@ -89,16 +89,15 @@ r_cpu被定义为当前CPU的最高性能水平与系统中任何其它CPU的最
  - Documentation/translations/zh_CN/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
 
 
-UTIL_EST / UTIL_EST_FASTUP
-==========================
+UTIL_EST
+========
 
 由于周期性任务的平均数在睡眠时会衰减，而在运行时其预期利用率会和睡眠前相同，
 因此它们在再次运行后会面临（DVFS）的上涨。
 
 为了缓解这个问题，（一个默认使能的编译选项）UTIL_EST驱动一个无限脉冲响应
 （Infinite Impulse Response，IIR）的EWMA，“运行”值在出队时是最高的。
-另一个默认使能的编译选项UTIL_EST_FASTUP修改了IIR滤波器，使其允许立即增加，
-仅在利用率下降时衰减。
+UTIL_EST滤波使其在遇到更高值时立刻增加，而遇到低值时会缓慢衰减。
 
 进一步，运行队列的（可运行任务的）利用率之和由下式计算：
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bcea3d55d95d..e94d65da8d66 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4870,11 +4870,9 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
 	 * to smooth utilization decreases.
 	 */
 	ue.enqueued = task_util(p);
-	if (sched_feat(UTIL_EST_FASTUP)) {
-		if (ue.ewma < ue.enqueued) {
-			ue.ewma = ue.enqueued;
-			goto done;
-		}
+	if (ue.ewma < ue.enqueued) {
+		ue.ewma = ue.enqueued;
+		goto done;
 	}
 
 	/*
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index a3ddf84de430..143f55df890b 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -83,7 +83,6 @@ SCHED_FEAT(WA_BIAS, true)
  * UtilEstimation. Use estimated CPU utilization.
  */
 SCHED_FEAT(UTIL_EST, true)
-SCHED_FEAT(UTIL_EST_FASTUP, true)
 
 SCHED_FEAT(LATENCY_WARN, false)
 
-- 
2.34.1

Re: [PATCH v2 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)

Posted by Alex Shi 2 years ago

Nice cleanup.

Reviewed-by: Alex Shi <alexs@kernel.org>

On Sat, Dec 2, 2023 at 12:17 AM Vincent Guittot
<vincent.guittot@linaro.org> wrote:
>
> sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature
> in order to check for possibly related regressions. After 3 years, it has
> never been used and no regression has been reported. Let remove it
> and make fast increase a permanent behavior.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> Reviewed-and-tested-by: Lukasz Luba <lukasz.luba@arm.com>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
> Reviewed-by: Tang Yizhou <yizhou.tang@shopee.com>
> ---
>  Documentation/scheduler/schedutil.rst                    | 7 +++----
>  Documentation/translations/zh_CN/scheduler/schedutil.rst | 7 +++----
>  kernel/sched/fair.c                                      | 8 +++-----
>  kernel/sched/features.h                                  | 1 -
>  4 files changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/scheduler/schedutil.rst b/Documentation/scheduler/schedutil.rst
> index 32c7d69fc86c..803fba8fc714 100644
> --- a/Documentation/scheduler/schedutil.rst
> +++ b/Documentation/scheduler/schedutil.rst
> @@ -90,8 +90,8 @@ For more detail see:
>   - Documentation/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
>
>
> -UTIL_EST / UTIL_EST_FASTUP
> -==========================
> +UTIL_EST
> +========
>
>  Because periodic tasks have their averages decayed while they sleep, even
>  though when running their expected utilization will be the same, they suffer a
> @@ -99,8 +99,7 @@ though when running their expected utilization will be the same, they suffer a
>
>  To alleviate this (a default enabled option) UTIL_EST drives an Infinite
>  Impulse Response (IIR) EWMA with the 'running' value on dequeue -- when it is
> -highest. A further default enabled option UTIL_EST_FASTUP modifies the IIR
> -filter to instantly increase and only decay on decrease.
> +highest. UTIL_EST filters to instantly increase and only decay on decrease.
>
>  A further runqueue wide sum (of runnable tasks) is maintained of:
>
> diff --git a/Documentation/translations/zh_CN/scheduler/schedutil.rst b/Documentation/translations/zh_CN/scheduler/schedutil.rst
> index d1ea68007520..7c8d87f21c42 100644
> --- a/Documentation/translations/zh_CN/scheduler/schedutil.rst
> +++ b/Documentation/translations/zh_CN/scheduler/schedutil.rst
> @@ -89,16 +89,15 @@ r_cpu被定义为当前CPU的最高性能水平与系统中任何其它CPU的最
>   - Documentation/translations/zh_CN/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
>
>
> -UTIL_EST / UTIL_EST_FASTUP
> -==========================
> +UTIL_EST
> +========
>
>  由于周期性任务的平均数在睡眠时会衰减，而在运行时其预期利用率会和睡眠前相同，
>  因此它们在再次运行后会面临（DVFS）的上涨。
>
>  为了缓解这个问题，（一个默认使能的编译选项）UTIL_EST驱动一个无限脉冲响应
>  （Infinite Impulse Response，IIR）的EWMA，“运行”值在出队时是最高的。
> -另一个默认使能的编译选项UTIL_EST_FASTUP修改了IIR滤波器，使其允许立即增加，
> -仅在利用率下降时衰减。
> +UTIL_EST滤波使其在遇到更高值时立刻增加，而遇到低值时会缓慢衰减。
>
>  进一步，运行队列的（可运行任务的）利用率之和由下式计算：
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index bcea3d55d95d..e94d65da8d66 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4870,11 +4870,9 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>          * to smooth utilization decreases.
>          */
>         ue.enqueued = task_util(p);
> -       if (sched_feat(UTIL_EST_FASTUP)) {
> -               if (ue.ewma < ue.enqueued) {
> -                       ue.ewma = ue.enqueued;
> -                       goto done;
> -               }
> +       if (ue.ewma < ue.enqueued) {
> +               ue.ewma = ue.enqueued;
> +               goto done;
>         }
>
>         /*
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index a3ddf84de430..143f55df890b 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -83,7 +83,6 @@ SCHED_FEAT(WA_BIAS, true)
>   * UtilEstimation. Use estimated CPU utilization.
>   */
>  SCHED_FEAT(UTIL_EST, true)
> -SCHED_FEAT(UTIL_EST_FASTUP, true)
>
>  SCHED_FEAT(LATENCY_WARN, false)
>
> --
> 2.34.1
>

Re: [PATCH v2 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)

Posted by Yanteng Si 2 years ago

在 2023/12/2 00:16, Vincent Guittot 写道:
> sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature
> in order to check for possibly related regressions. After 3 years, it has
> never been used and no regression has been reported. Let remove it
> and make fast increase a permanent behavior.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> Reviewed-and-tested-by: Lukasz Luba <lukasz.luba@arm.com>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
> Reviewed-by: Tang Yizhou <yizhou.tang@shopee.com>

For Chinese translation,


Reviewed-by: Yanteng Si <siyanteng@loongson.cn>


Thanks,

Yanteng

> ---
>   Documentation/scheduler/schedutil.rst                    | 7 +++----
>   Documentation/translations/zh_CN/scheduler/schedutil.rst | 7 +++----
>   kernel/sched/fair.c                                      | 8 +++-----
>   kernel/sched/features.h                                  | 1 -
>   4 files changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/scheduler/schedutil.rst b/Documentation/scheduler/schedutil.rst
> index 32c7d69fc86c..803fba8fc714 100644
> --- a/Documentation/scheduler/schedutil.rst
> +++ b/Documentation/scheduler/schedutil.rst
> @@ -90,8 +90,8 @@ For more detail see:
>    - Documentation/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
>   
>   
> -UTIL_EST / UTIL_EST_FASTUP
> -==========================
> +UTIL_EST
> +========
>   
>   Because periodic tasks have their averages decayed while they sleep, even
>   though when running their expected utilization will be the same, they suffer a
> @@ -99,8 +99,7 @@ though when running their expected utilization will be the same, they suffer a
>   
>   To alleviate this (a default enabled option) UTIL_EST drives an Infinite
>   Impulse Response (IIR) EWMA with the 'running' value on dequeue -- when it is
> -highest. A further default enabled option UTIL_EST_FASTUP modifies the IIR
> -filter to instantly increase and only decay on decrease.
> +highest. UTIL_EST filters to instantly increase and only decay on decrease.
>   
>   A further runqueue wide sum (of runnable tasks) is maintained of:
>   
> diff --git a/Documentation/translations/zh_CN/scheduler/schedutil.rst b/Documentation/translations/zh_CN/scheduler/schedutil.rst
> index d1ea68007520..7c8d87f21c42 100644
> --- a/Documentation/translations/zh_CN/scheduler/schedutil.rst
> +++ b/Documentation/translations/zh_CN/scheduler/schedutil.rst
> @@ -89,16 +89,15 @@ r_cpu被定义为当前CPU的最高性能水平与系统中任何其它CPU的最
>    - Documentation/translations/zh_CN/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
>   
>   
> -UTIL_EST / UTIL_EST_FASTUP
> -==========================
> +UTIL_EST
> +========
>   
>   由于周期性任务的平均数在睡眠时会衰减，而在运行时其预期利用率会和睡眠前相同，
>   因此它们在再次运行后会面临（DVFS）的上涨。
>   
>   为了缓解这个问题，（一个默认使能的编译选项）UTIL_EST驱动一个无限脉冲响应
>   （Infinite Impulse Response，IIR）的EWMA，“运行”值在出队时是最高的。
> -另一个默认使能的编译选项UTIL_EST_FASTUP修改了IIR滤波器，使其允许立即增加，
> -仅在利用率下降时衰减。
> +UTIL_EST滤波使其在遇到更高值时立刻增加，而遇到低值时会缓慢衰减。
>   
>   进一步，运行队列的（可运行任务的）利用率之和由下式计算：
>   
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index bcea3d55d95d..e94d65da8d66 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4870,11 +4870,9 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>   	 * to smooth utilization decreases.
>   	 */
>   	ue.enqueued = task_util(p);
> -	if (sched_feat(UTIL_EST_FASTUP)) {
> -		if (ue.ewma < ue.enqueued) {
> -			ue.ewma = ue.enqueued;
> -			goto done;
> -		}
> +	if (ue.ewma < ue.enqueued) {
> +		ue.ewma = ue.enqueued;
> +		goto done;
>   	}
>   
>   	/*
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index a3ddf84de430..143f55df890b 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -83,7 +83,6 @@ SCHED_FEAT(WA_BIAS, true)
>    * UtilEstimation. Use estimated CPU utilization.
>    */
>   SCHED_FEAT(UTIL_EST, true)
> -SCHED_FEAT(UTIL_EST_FASTUP, true)
>   
>   SCHED_FEAT(LATENCY_WARN, false)
>

[tip: sched/core] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)

Posted by tip-bot2 for Vincent Guittot 1 year, 11 months ago

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

Commit-ID:     7736ae5572eb344c090fbef9621a228e7e3d6276
Gitweb:        https://git.kernel.org/tip/7736ae5572eb344c090fbef9621a228e7e3d6276
Author:        Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate:    Fri, 01 Dec 2023 17:16:51 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Dec 2023 15:59:56 +01:00

sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)

sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature
in order to check for possibly related regressions. After 3 years, it has
never been used and no regression has been reported. Let's remove it
and make fast increase a permanent behavior.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
Reviewed-by: Tang Yizhou <yizhou.tang@shopee.com>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn> [for the Chinese translation]
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/20231201161652.1241695-2-vincent.guittot@linaro.org
---
 Documentation/scheduler/schedutil.rst                    | 7 +++----
 Documentation/translations/zh_CN/scheduler/schedutil.rst | 7 +++----
 kernel/sched/fair.c                                      | 8 +++-----
 kernel/sched/features.h                                  | 1 +-
 4 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/Documentation/scheduler/schedutil.rst b/Documentation/scheduler/schedutil.rst
index 32c7d69..803fba8 100644
--- a/Documentation/scheduler/schedutil.rst
+++ b/Documentation/scheduler/schedutil.rst
@@ -90,8 +90,8 @@ For more detail see:
  - Documentation/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
 
 
-UTIL_EST / UTIL_EST_FASTUP
-==========================
+UTIL_EST
+========
 
 Because periodic tasks have their averages decayed while they sleep, even
 though when running their expected utilization will be the same, they suffer a
@@ -99,8 +99,7 @@ though when running their expected utilization will be the same, they suffer a
 
 To alleviate this (a default enabled option) UTIL_EST drives an Infinite
 Impulse Response (IIR) EWMA with the 'running' value on dequeue -- when it is
-highest. A further default enabled option UTIL_EST_FASTUP modifies the IIR
-filter to instantly increase and only decay on decrease.
+highest. UTIL_EST filters to instantly increase and only decay on decrease.
 
 A further runqueue wide sum (of runnable tasks) is maintained of:
 
diff --git a/Documentation/translations/zh_CN/scheduler/schedutil.rst b/Documentation/translations/zh_CN/scheduler/schedutil.rst
index d1ea680..7c8d87f 100644
--- a/Documentation/translations/zh_CN/scheduler/schedutil.rst
+++ b/Documentation/translations/zh_CN/scheduler/schedutil.rst
@@ -89,16 +89,15 @@ r_cpu被定义为当前CPU的最高性能水平与系统中任何其它CPU的最
  - Documentation/translations/zh_CN/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization"
 
 
-UTIL_EST / UTIL_EST_FASTUP
-==========================
+UTIL_EST
+========
 
 由于周期性任务的平均数在睡眠时会衰减，而在运行时其预期利用率会和睡眠前相同，
 因此它们在再次运行后会面临（DVFS）的上涨。
 
 为了缓解这个问题，（一个默认使能的编译选项）UTIL_EST驱动一个无限脉冲响应
 （Infinite Impulse Response，IIR）的EWMA，“运行”值在出队时是最高的。
-另一个默认使能的编译选项UTIL_EST_FASTUP修改了IIR滤波器，使其允许立即增加，
-仅在利用率下降时衰减。
+UTIL_EST滤波使其在遇到更高值时立刻增加，而遇到低值时会缓慢衰减。
 
 进一步，运行队列的（可运行任务的）利用率之和由下式计算：
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bcea3d5..e94d65d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4870,11 +4870,9 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
 	 * to smooth utilization decreases.
 	 */
 	ue.enqueued = task_util(p);
-	if (sched_feat(UTIL_EST_FASTUP)) {
-		if (ue.ewma < ue.enqueued) {
-			ue.ewma = ue.enqueued;
-			goto done;
-		}
+	if (ue.ewma < ue.enqueued) {
+		ue.ewma = ue.enqueued;
+		goto done;
 	}
 
 	/*
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index a3ddf84..143f55d 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -83,7 +83,6 @@ SCHED_FEAT(WA_BIAS, true)
  * UtilEstimation. Use estimated CPU utilization.
  */
 SCHED_FEAT(UTIL_EST, true)
-SCHED_FEAT(UTIL_EST_FASTUP, true)
 
 SCHED_FEAT(LATENCY_WARN, false)

[PATCH v2 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true)
[PATCH v2 2/2] sched/fair: Simplify util_est