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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 2D154C4321E for ; Mon, 10 Sep 2018 10:18:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1539020865 for ; Mon, 10 Sep 2018 10:18:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1539020865 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728320AbeIJPLU (ORCPT ); Mon, 10 Sep 2018 11:11:20 -0400 Received: from terminus.zytor.com ([198.137.202.136]:39513 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728210AbeIJPLU (ORCPT ); Mon, 10 Sep 2018 11:11:20 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w8AAHcBE1808381 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 10 Sep 2018 03:17:38 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w8AAHcEE1808378; Mon, 10 Sep 2018 03:17:38 -0700 Date: Mon, 10 Sep 2018 03:17:38 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Valentin Schneider Message-ID: Cc: valentin.schneider@arm.com, hpa@zytor.com, peterz@infradead.org, torvalds@linux-foundation.org, tglx@linutronix.de, morten.rasmussen@arm.com, mingo@kernel.org, linux-kernel@vger.kernel.org Reply-To: mingo@kernel.org, linux-kernel@vger.kernel.org, morten.rasmussen@arm.com, tglx@linutronix.de, torvalds@linux-foundation.org, peterz@infradead.org, hpa@zytor.com, valentin.schneider@arm.com In-Reply-To: <1530699470-29808-10-git-send-email-morten.rasmussen@arm.com> References: <1530699470-29808-10-git-send-email-morten.rasmussen@arm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: Set rq->rd->overload when misfit Git-Commit-ID: 757ffdd705ee942fc8150b17942d968601d2a15b X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 757ffdd705ee942fc8150b17942d968601d2a15b Gitweb: https://git.kernel.org/tip/757ffdd705ee942fc8150b17942d968601d2a15b Author: Valentin Schneider AuthorDate: Wed, 4 Jul 2018 11:17:47 +0100 Committer: Ingo Molnar CommitDate: Mon, 10 Sep 2018 11:05:53 +0200 sched/fair: Set rq->rd->overload when misfit Idle balance is a great opportunity to pull a misfit task. However, there are scenarios where misfit tasks are present but idle balance is prevented by the overload flag. A good example of this is a workload of n identical tasks. Let's suppose we have a 2+2 Arm big.LITTLE system. We then spawn 4 fairly CPU-intensive tasks - for the sake of simplicity let's say they are just CPU hogs, even when running on big CPUs. They are identical tasks, so on an SMP system they should all end at (roughly) the same time. However, in our case the LITTLE CPUs are less performing than the big CPUs, so tasks running on the LITTLEs will have a longer completion time. This means that the big CPUs will complete their work earlier, at which point they should pull the tasks from the LITTLEs. What we want to happen is summarized as follows: a,b,c,d are our CPU-hogging tasks _ signifies idling LITTLE_0 | a a a a _ _ LITTLE_1 | b b b b _ _ ---------|------------- big_0 | c c c c a a big_1 | d d d d b b ^ ^ Tasks end on the big CPUs, idle balance happens and the misfit tasks are pulled straight away This however won't happen, because currently the overload flag is only set when there is any CPU that has more than one runnable task - which may very well not be the case here if our CPU-hogging workload is all there is to run. As such, this commit sets the overload flag in update_sg_lb_stats when a group is flagged as having a misfit task. Signed-off-by: Valentin Schneider Signed-off-by: Morten Rasmussen Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dietmar.eggemann@arm.com Cc: gaku.inami.xh@renesas.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1530699470-29808-10-git-send-email-morten.rasmussen@arm.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 6 ++++-- kernel/sched/sched.h | 6 +++++- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d9c4e97bfebd..8b228c5b3eb4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7793,7 +7793,7 @@ static bool update_nohz_stats(struct rq *rq, bool force) * @load_idx: Load index of sched_domain of this_cpu for load calc. * @local_group: Does group contain this_cpu. * @sgs: variable to hold the statistics for this group. - * @overload: Indicate more than one runnable task for any CPU. + * @overload: Indicate pullable load (e.g. >1 runnable task). */ static inline void update_sg_lb_stats(struct lb_env *env, struct sched_group *group, int load_idx, @@ -7837,8 +7837,10 @@ static inline void update_sg_lb_stats(struct lb_env *env, sgs->idle_cpus++; if (env->sd->flags & SD_ASYM_CPUCAPACITY && - sgs->group_misfit_task_load < rq->misfit_task_load) + sgs->group_misfit_task_load < rq->misfit_task_load) { sgs->group_misfit_task_load = rq->misfit_task_load; + *overload = 1; + } } /* Adjust by relative CPU capacity of the group */ diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 938063639793..85b3a2bf6c2b 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -715,7 +715,11 @@ struct root_domain { cpumask_var_t span; cpumask_var_t online; - /* Indicate more than one runnable task for any CPU */ + /* + * Indicate pullable load on at least one CPU, e.g: + * - More than one runnable task + * - Running task is misfit + */ int overload; /*