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([2a01:e0a:f:6020:cc67:4d1a:fe5d:819a]) by smtp.gmail.com with ESMTPSA id i2-20020adffc02000000b0032f7f4089b7sm12174392wrr.43.2023.11.27.06.32.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Nov 2023 06:32:45 -0800 (PST) From: Vincent Guittot To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, corbet@lwn.net, alexs@kernel.org, siyanteng@loongson.cn, qyousef@layalina.io, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: lukasz.luba@arm.com, hongyan.xia2@arm.com, Vincent Guittot Subject: [PATCH 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true) Date: Mon, 27 Nov 2023 15:32:37 +0100 Message-Id: <20231127143238.1216582-2-vincent.guittot@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231127143238.1216582-1-vincent.guittot@linaro.org> References: <20231127143238.1216582-1-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on howler.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Mon, 27 Nov 2023 06:35:38 -0800 (PST) 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 --- I haven't updated the chinese documentation which also refers to UTIL_EST_FASTUP. IIUC, this will be updated afterward by the Translations' maintainers. Documentation/scheduler/schedutil.rst | 7 +++---- kernel/sched/fair.c | 8 +++----- kernel/sched/features.h | 1 - 3 files changed, 6 insertions(+), 10 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/kernel/sched/fair.c b/kernel/sched/fair.c index 34fe6e9490c2..146329678cb8 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