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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 A8678C43603 for ; Wed, 11 Dec 2019 11:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 836892073D for ; Wed, 11 Dec 2019 11:39:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729113AbfLKLjY (ORCPT ); Wed, 11 Dec 2019 06:39:24 -0500 Received: from foss.arm.com ([217.140.110.172]:55042 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729098AbfLKLjV (ORCPT ); Wed, 11 Dec 2019 06:39:21 -0500 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 4A2E931B; Wed, 11 Dec 2019 03:39:21 -0800 (PST) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id EE0DD3F6CF; Wed, 11 Dec 2019 03:39:19 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, patrick.bellasi@matbug.net, qperret@google.com, qais.yousef@arm.com, morten.rasmussen@arm.com Subject: [PATCH v3 5/5] sched/fair: Make EAS wakeup placement consider uclamp restrictions Date: Wed, 11 Dec 2019 11:38:51 +0000 Message-Id: <20191211113851.24241-6-valentin.schneider@arm.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191211113851.24241-1-valentin.schneider@arm.com> References: <20191211113851.24241-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org task_fits_capacity() has just been made uclamp-aware, and find_energy_efficient_cpu() needs to go through the same treatment. Things are somewhat different here however - using the task max clamp isn't sufficient. Consider the following setup: The target runqueue, rq: rq.cpu_capacity_orig = 512 rq.cfs.avg.util_avg = 200 rq.uclamp.max = 768 // the max p.uclamp.max of all enqueued p's is 768 The waking task, p (not yet enqueued on rq): p.util_est = 600 p.uclamp.max = 100 Now, consider the following code which doesn't use the rq clamps: util = uclamp_task_util(p); // Does the task fit in the spare CPU capacity? cpu = cpu_of(rq); fits_capacity(util, cpu_capacity(cpu) - cpu_util(cpu)) This would lead to: util = 100; fits_capacity(100, 512 - 200) fits_capacity() would return true. However, enqueuing p on that CPU *will* cause it to become overutilized since rq clamp values are max-aggregated, so we'd remain with rq.uclamp.max = 768 which comes from the other tasks already enqueued on rq. Thus, we could select a high enough frequency to reach beyond 0.8 * 512 utilization (== overutilized) after enqueuing p on rq. What find_energy_efficient_cpu() needs here is uclamp_rq_util_with() which lets us peek at the future utilization landscape, including rq-wide uclamp values. Make find_energy_efficient_cpu() use uclamp_rq_util_with() for its fits_capacity() check. This is in line with what compute_energy() ends up using for estimating utilization. Suggested-by: Quentin Perret Reviewed-by: Vincent Guittot Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a9c93c5427bf..956d9578935a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6282,9 +6282,18 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) if (!cpumask_test_cpu(cpu, p->cpus_ptr)) continue; - /* Skip CPUs that will be overutilized. */ util = cpu_util_next(cpu, p, cpu); cpu_cap = capacity_of(cpu); + spare_cap = cpu_cap - util; + + /* + * Skip CPUs that cannot satisfy the capacity request. + * IOW, placing the task there would make the CPU + * overutilized. Take uclamp into account to see how + * much capacity we can get out of the CPU; this is + * aligned with schedutil_cpu_util(). + */ + util = uclamp_rq_util_with(cpu_rq(cpu), util, p); if (!fits_capacity(util, cpu_cap)) continue; @@ -6299,7 +6308,6 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) * Find the CPU with the maximum spare capacity in * the performance domain */ - spare_cap = cpu_cap - util; if (spare_cap > max_spare_cap) { max_spare_cap = spare_cap; max_spare_cap_cpu = cpu; -- 2.24.0