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 X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E94FC433ED for ; Tue, 4 May 2021 09:08:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07747610A1 for ; Tue, 4 May 2021 09:08:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230112AbhEDJJL (ORCPT ); Tue, 4 May 2021 05:09:11 -0400 Received: from foss.arm.com ([217.140.110.172]:55962 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230025AbhEDJJH (ORCPT ); Tue, 4 May 2021 05:09:07 -0400 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 0BE9C1063; Tue, 4 May 2021 02:08:13 -0700 (PDT) Received: from e120189.arm.com (unknown [10.57.63.61]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D14463F73B; Tue, 4 May 2021 02:08:09 -0700 (PDT) From: Pierre Gondois To: linux-kernel@vger.kernel.org, xuewen.yan@unisoc.com, qperret@qperret.net, Lukasz.Luba@arm.com, dietmar.eggemann@arm.com Cc: Vincent.Donnefort@arm.com, Pierre Gondois , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com Subject: [PATCH v3 1/2] sched/fair: Only compute base_energy_pd if necessary Date: Tue, 4 May 2021 10:07:42 +0100 Message-Id: <20210504090743.9688-2-Pierre.Gondois@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210504090743.9688-1-Pierre.Gondois@arm.com> References: <20210504090743.9688-1-Pierre.Gondois@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org find_energy_efficient_cpu() searches the best energy CPU to place a task on. To do so, the energy of each performance domain (pd) is computed w/ and w/o the task placed on it. The energy of a pd w/o the task (base_energy_pd) is computed prior knowing whether a CPU is available in the pd. Move the base_energy_pd computation after looping through the CPUs of a pd and only compute it if at least one CPU is available. Suggested-by: Xuewen Yan Signed-off-by: Pierre Gondois Reviewed-by: Dietmar Eggemann Reviewed-by: Lukasz Luba --- kernel/sched/fair.c | 41 ++++++++++++++++++++++++----------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0dba0ebc3657..fcb9595fc123 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6620,13 +6620,10 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) for (; pd; pd = pd->next) { unsigned long cur_delta, spare_cap, max_spare_cap = 0; + bool compute_prev_delta = false; unsigned long base_energy_pd; int max_spare_cap_cpu = -1; - /* Compute the 'base' energy of the pd, without @p */ - base_energy_pd = compute_energy(p, -1, pd); - base_energy += base_energy_pd; - for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) { if (!cpumask_test_cpu(cpu, p->cpus_ptr)) continue; @@ -6647,25 +6644,35 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) if (!fits_capacity(util, cpu_cap)) continue; - /* Always use prev_cpu as a candidate. */ if (cpu == prev_cpu) { - prev_delta = compute_energy(p, prev_cpu, pd); - prev_delta -= base_energy_pd; - best_delta = min(best_delta, prev_delta); - } - - /* - * Find the CPU with the maximum spare capacity in - * the performance domain - */ - if (spare_cap > max_spare_cap) { + /* Always use prev_cpu as a candidate. */ + compute_prev_delta = true; + } else if (spare_cap > max_spare_cap) { + /* + * Find the CPU with the maximum spare capacity + * in the performance domain. + */ max_spare_cap = spare_cap; max_spare_cap_cpu = cpu; } } - /* Evaluate the energy impact of using this CPU. */ - if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) { + if (max_spare_cap_cpu < 0 && !compute_prev_delta) + continue; + + /* Compute the 'base' energy of the pd, without @p */ + base_energy_pd = compute_energy(p, -1, 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 -= base_energy_pd; + best_delta = min(best_delta, prev_delta); + } + + /* 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 -= base_energy_pd; if (cur_delta < best_delta) { -- 2.17.1