From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B505C433F5 for ; Wed, 27 Apr 2022 14:33:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238171AbiD0Og6 (ORCPT ); Wed, 27 Apr 2022 10:36:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238126AbiD0Ogi (ORCPT ); Wed, 27 Apr 2022 10:36:38 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C29BF7669 for ; Wed, 27 Apr 2022 07:33:24 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D30FA1477; Wed, 27 Apr 2022 07:33:23 -0700 (PDT) Received: from localhost.localdomain (unknown [10.57.44.232]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 618823F5A1; Wed, 27 Apr 2022 07:33:22 -0700 (PDT) From: Vincent Donnefort To: peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org Cc: linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, qperret@google.com Subject: [PATCH v7 5/7] sched/fair: Use the same cpumask per-PD throughout find_energy_efficient_cpu() Date: Wed, 27 Apr 2022 15:33:02 +0100 Message-Id: <20220427143304.3950488-6-vincent.donnefort@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220427143304.3950488-1-vincent.donnefort@arm.com> References: <20220427143304.3950488-1-vincent.donnefort@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dietmar Eggemann The Perf Domain (PD) cpumask (struct em_perf_domain.cpus) stays invariant after Energy Model creation, i.e. it is not updated after CPU hotplug operations. That's why the PD mask is used in conjunction with the cpu_online_mask (or Sched Domain cpumask). Thereby the cpu_online_mask is fetched multiple times (in compute_energy()) during a run-queue selection for a task. cpu_online_mask may change during this time which can lead to wrong energy calculations. To be able to avoid this, use the select_rq_mask per-cpu cpumask to create a cpumask out of PD cpumask and cpu_online_mask and pass it through the function calls of the EAS run-queue selection path. The PD cpumask for max_spare_cap_cpu/compute_prev_delta selection (find_energy_efficient_cpu()) is now ANDed not only with the SD mask but also with the cpu_online_mask. This is fine since this cpumask has to be in syc with the one used for energy computation (compute_energy()). An exclusive cpuset setup with at least one asymmetric CPU capacity island (hence the additional AND with the SD cpumask) is the obvious exception here. Signed-off-by: Dietmar Eggemann diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a4ad4d82f217..d705298aa310 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6696,14 +6696,14 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu) * task. */ static long -compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) +compute_energy(struct task_struct *p, int dst_cpu, struct cpumask *cpus, + struct perf_domain *pd) { - struct cpumask *pd_mask = perf_domain_span(pd); unsigned long max_util = 0, sum_util = 0, cpu_cap; int cpu; - cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask)); - cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask)); + cpu_cap = arch_scale_cpu_capacity(cpumask_first(cpus)); + cpu_cap -= arch_scale_thermal_pressure(cpumask_first(cpus)); /* * The capacity state of CPUs of the current rd can be driven by CPUs @@ -6714,7 +6714,7 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) * If an entire pd is outside of the current rd, it will not appear in * its pd list and will not be accounted by compute_energy(). */ - for_each_cpu_and(cpu, pd_mask, cpu_online_mask) { + for_each_cpu(cpu, cpus) { unsigned long util_freq = cpu_util_next(cpu, p, dst_cpu); unsigned long cpu_util, util_running = util_freq; struct task_struct *tsk = NULL; @@ -6801,6 +6801,7 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) */ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) { + struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask); unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX; struct root_domain *rd = cpu_rq(smp_processor_id())->rd; int cpu, best_energy_cpu = prev_cpu, target = -1; @@ -6835,7 +6836,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) unsigned long base_energy_pd; int max_spare_cap_cpu = -1; - for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) { + cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask); + + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) { if (!cpumask_test_cpu(cpu, p->cpus_ptr)) continue; @@ -6872,12 +6875,12 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) continue; /* Compute the 'base' energy of the pd, without @p */ - base_energy_pd = compute_energy(p, -1, pd); + base_energy_pd = compute_energy(p, -1, cpus, pd); base_energy += base_energy_pd; /* Evaluate the energy impact of using prev_cpu. */ if (compute_prev_delta) { - prev_delta = compute_energy(p, prev_cpu, pd); + prev_delta = compute_energy(p, prev_cpu, cpus, pd); if (prev_delta < base_energy_pd) goto unlock; prev_delta -= base_energy_pd; @@ -6886,7 +6889,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) /* Evaluate the energy impact of using max_spare_cap_cpu. */ if (max_spare_cap_cpu >= 0) { - cur_delta = compute_energy(p, max_spare_cap_cpu, pd); + cur_delta = compute_energy(p, max_spare_cap_cpu, cpus, + pd); if (cur_delta < base_energy_pd) goto unlock; cur_delta -= base_energy_pd; -- 2.25.1