Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753266AbdLERKv (ORCPT ); Tue, 5 Dec 2017 12:10:51 -0500 Received: from foss.arm.com ([217.140.101.70]:52344 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753042AbdLERKt (ORCPT ); Tue, 5 Dec 2017 12:10:49 -0500 From: Patrick Bellasi To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes Subject: [PATCH v2 4/4] sched/cpufreq_schedutil: use util_est for OPP selection Date: Tue, 5 Dec 2017 17:10:18 +0000 Message-Id: <20171205171018.9203-5-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171205171018.9203-1-patrick.bellasi@arm.com> References: <20171205171018.9203-1-patrick.bellasi@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2750 Lines: 68 When schedutil looks at the CPU utilization, the current PELT value for that CPU is returned straight away. In certain scenarios this can have undesired side effects and delays on frequency selection. For example, since the task utilization is decayed at wakeup time, a long sleeping big task newly enqueued does not add immediately a significant contribution to the target CPU. This introduces some latency before schedutil will be able to detect the best frequency required by that task. Moreover, the PELT signal build-up time is function of the current frequency, because of the scale invariant load tracking support. Thus, starting from a lower frequency, the utilization build-up time will increase even more and further delays the selection of the actual frequency which better serves the task requirements. In order to reduce these kind of latencies, this patch integrates the usage of the CPU's estimated utilization in the sugov_get_util function. The estimated utilization of a CPU is defined to be the maximum between its PELT's utilization and the sum of the estimated utilization of each currently RUNNABLE task on that CPU. This allows to properly represent the expected utilization of a CPU which, for example, has just got a big task running after a long sleep period, and ultimately it allows to select the best frequency to run a task right after it wakes up. Signed-off-by: Patrick Bellasi Reviewed-by: Brendan Jackman Reviewed-by: Dietmar Eggemann Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Viresh Kumar Cc: Paul Turner Cc: Vincent Guittot Cc: Morten Rasmussen Cc: Dietmar Eggemann Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- Changes v1->v2: - rebase on top of v4.15-rc2 - tested that overhauled PELT code does not affect the util_est --- kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 2f52ec0f1539..465430d99440 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -183,7 +183,11 @@ static void sugov_get_util(unsigned long *util, unsigned long *max, int cpu) cfs_max = arch_scale_cpu_capacity(NULL, cpu); - *util = min(rq->cfs.avg.util_avg, cfs_max); + *util = rq->cfs.avg.util_avg; + if (sched_feat(UTIL_EST)) + *util = max(*util, rq->cfs.util_est_runnable); + *util = min(*util, cfs_max); + *max = cfs_max; } -- 2.14.1