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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 6D626C43381 for ; Sat, 9 Mar 2019 14:37:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F5E7207E0 for ; Sat, 9 Mar 2019 14:37:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726551AbfCIOhv (ORCPT ); Sat, 9 Mar 2019 09:37:51 -0500 Received: from terminus.zytor.com ([198.137.202.136]:38867 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726294AbfCIOhv (ORCPT ); Sat, 9 Mar 2019 09:37:51 -0500 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x29EbXhB3108947 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sat, 9 Mar 2019 06:37:33 -0800 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x29EbVRN3108942; Sat, 9 Mar 2019 06:37:31 -0800 Date: Sat, 9 Mar 2019 06:37:31 -0800 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Valentin Schneider Message-ID: Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, riel@surriel.com, dave.hansen@linux.intel.com, peterz@infradead.org, hpa@zytor.com, valentin.schneider@arm.com, bp@alien8.de, luto@kernel.org, torvalds@linux-foundation.org Reply-To: torvalds@linux-foundation.org, luto@kernel.org, bp@alien8.de, valentin.schneider@arm.com, peterz@infradead.org, hpa@zytor.com, dave.hansen@linux.intel.com, riel@surriel.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org In-Reply-To: <20190211175946.4961-3-valentin.schneider@arm.com> References: <20190211175946.4961-3-valentin.schneider@arm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/fair: Tune down misfit NOHZ kicks Git-Commit-ID: 88a2f7ffd19245a75143a8180f75c0972cff0350 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: 88a2f7ffd19245a75143a8180f75c0972cff0350 Gitweb: https://git.kernel.org/tip/88a2f7ffd19245a75143a8180f75c0972cff0350 Author: Valentin Schneider AuthorDate: Mon, 11 Feb 2019 17:59:45 +0000 Committer: Ingo Molnar CommitDate: Sat, 9 Mar 2019 14:03:53 +0100 sched/fair: Tune down misfit NOHZ kicks In this commit: 3b1baa6496e6 ("sched/fair: Add 'group_misfit_task' load-balance type") we set rq->misfit_task_load whenever the current running task has a utilization greater than 80% of rq->cpu_capacity. A non-zero value in this field enables misfit load balancing. However, if the task being looked at is already running on a CPU of highest capacity, there's nothing more we can do for it. We can currently spot this in update_sd_pick_busiest(), which prevents us from selecting a sched_group of group_type == group_misfit_task as the busiest group, but we don't do any of that in nohz_balancer_kick(). This means that we could repeatedly kick NOHZ CPUs when there's no improvements in terms of load balance to be done. Introduce a check_misfit_status() helper that returns true iff there is a CPU in the system that could give more CPU capacity to a rq's misfit task - IOW, there exists a CPU of higher capacity_orig or the rq's CPU is severely pressured by rt/IRQ. Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Dietmar.Eggemann@arm.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: morten.rasmussen@arm.com Cc: vincent.guittot@linaro.org Link: https://lkml.kernel.org/r/20190211175946.4961-3-valentin.schneider@arm.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e6f7d39d4d45..f0d2f8a352bf 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8058,6 +8058,18 @@ check_cpu_capacity(struct rq *rq, struct sched_domain *sd) (rq->cpu_capacity_orig * 100)); } +/* + * Check whether a rq has a misfit task and if it looks like we can actually + * help that task: we can migrate the task to a CPU of higher capacity, or + * the task's current CPU is heavily pressured. + */ +static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd) +{ + return rq->misfit_task_load && + (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity || + check_cpu_capacity(rq, sd)); +} + /* * Group imbalance indicates (and tries to solve) the problem where balancing * groups is inadequate due to ->cpus_allowed constraints. @@ -9585,7 +9597,7 @@ static void nohz_balancer_kick(struct rq *rq) if (time_before(now, nohz.next_balance)) goto out; - if (rq->nr_running >= 2 || rq->misfit_task_load) { + if (rq->nr_running >= 2) { flags = NOHZ_KICK_MASK; goto out; } @@ -9623,6 +9635,18 @@ static void nohz_balancer_kick(struct rq *rq) } } + sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu)); + if (sd) { + /* + * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU + * to run the misfit task on. + */ + if (check_misfit_status(rq, sd)) { + flags = NOHZ_KICK_MASK; + goto unlock; + } + } + sd = rcu_dereference(per_cpu(sd_asym_packing, cpu)); if (sd) { /*