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Message-ID: <30b94fb1-7794-4dc4-8af3-65703b4fab81@loongson.cn> Date: Sat, 2 Dec 2023 10:41:40 +0800 From: Yanteng Si <siyanteng@...ngson.cn> To: Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com, corbet@....net, alexs@...nel.org, qyousef@...alina.io, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org Cc: lukasz.luba@....com, hongyan.xia2@....com, yizhou.tang@...pee.com Subject: Re: [PATCH v2 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true) 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@...aro.org> > Reviewed-and-tested-by: Lukasz Luba <lukasz.luba@....com> > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com> > Reviewed-by: Hongyan Xia <hongyan.xia2@....com> > Reviewed-by: Tang Yizhou <yizhou.tang@...pee.com> For Chinese translation, Reviewed-by: Yanteng Si <siyanteng@...ngson.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) >
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