From patchwork Wed Aug 31 10:52:18 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Morten Rasmussen X-Patchwork-Id: 75072 Delivered-To: patch@linaro.org Received: by 10.140.29.52 with SMTP id a49csp265020qga; Wed, 31 Aug 2016 03:52:42 -0700 (PDT) X-Received: by 10.98.138.153 with SMTP id o25mr15680445pfk.80.1472640757288; Wed, 31 Aug 2016 03:52:37 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id cq3si50316738pad.61.2016.08.31.03.52.37; Wed, 31 Aug 2016 03:52:37 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760320AbcHaKw0 (ORCPT + 27 others); Wed, 31 Aug 2016 06:52:26 -0400 Received: from foss.arm.com ([217.140.101.70]:57664 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759934AbcHaKwT (ORCPT ); Wed, 31 Aug 2016 06:52:19 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EF0FBCF4; Wed, 31 Aug 2016 03:52:13 -0700 (PDT) Received: from e105550-lin.cambridge.arm.com (e105550-lin.cambridge.arm.com [10.1.211.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 45C113F220; Wed, 31 Aug 2016 03:52:12 -0700 (PDT) From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: dietmar.eggemann@arm.com, yuyang.du@intel.com, vincent.guittot@linaro.org, mgalbraith@suse.de, sgurrappadi@nvidia.com, freedom.tan@mediatek.com, keita.kobayashi.ym@renesas.com, linux-kernel@vger.kernel.org, Morten Rasmussen Subject: [PATCH v4 4/5] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups Date: Wed, 31 Aug 2016 11:52:18 +0100 Message-Id: <1472640739-8778-5-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1472640739-8778-1-git-send-email-morten.rasmussen@arm.com> References: <1472640739-8778-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For asymmetric cpu capacity systems it is counter-productive for throughput if low capacity cpus are pulling tasks from non-overloaded cpus with higher capacity. The assumption is that higher cpu capacity is preferred over running alone in a group with lower cpu capacity. This patch rejects higher cpu capacity groups with one or less task per cpu as potential busiest group which could otherwise lead to a series of failing load-balancing attempts leading to a force-migration. cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- kernel/sched/fair.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) -- 1.9.1 diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 112a6d3f3943..68d8b40c546b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6878,6 +6878,17 @@ group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) return false; } +/* + * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller + * per-cpu capacity than sched_group ref. + */ +static inline bool +group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref) +{ + return sg->sgc->min_capacity * capacity_margin < + ref->sgc->min_capacity * 1024; +} + static inline enum group_type group_classify(struct sched_group *group, struct sg_lb_stats *sgs) @@ -6981,6 +6992,20 @@ static bool update_sd_pick_busiest(struct lb_env *env, if (sgs->avg_load <= busiest->avg_load) return false; + if (!(env->sd->flags & SD_ASYM_CPUCAPACITY)) + goto asym_packing; + + /* + * Candidate sg has no more than one task per cpu and + * has higher per-cpu capacity. Migrating tasks to less + * capable cpus may harm throughput. Maximize throughput, + * power/energy consequences are not considered. + */ + if (sgs->sum_nr_running <= sgs->group_weight && + group_smaller_cpu_capacity(sds->local, sg)) + return false; + +asym_packing: /* This is the busiest node in its class. */ if (!(env->sd->flags & SD_ASYM_PACKING)) return true;