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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 0A341C43444 for ; Thu, 17 Jan 2019 15:37:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7DAE20652 for ; Thu, 17 Jan 2019 15:37:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728220AbfAQPho (ORCPT ); Thu, 17 Jan 2019 10:37:44 -0500 Received: from foss.arm.com ([217.140.101.70]:42026 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728120AbfAQPhm (ORCPT ); Thu, 17 Jan 2019 10:37:42 -0500 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 6D3D2165C; Thu, 17 Jan 2019 07:37:42 -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 177233F819; Thu, 17 Jan 2019 07:37:40 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, morten.rasmussen@arm.com, Dietmar.Eggemann@arm.com Subject: [PATCH 4/5] sched/fair: Tune down misfit nohz kicks Date: Thu, 17 Jan 2019 15:34:10 +0000 Message-Id: <20190117153411.2390-5-valentin.schneider@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190117153411.2390-1-valentin.schneider@arm.com> References: <20190117153411.2390-1-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 In commmit 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 --- kernel/sched/fair.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7658f9d76a9a..291dfdb0183f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8012,6 +8012,18 @@ 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. @@ -9527,7 +9539,7 @@ 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; } @@ -9561,6 +9573,14 @@ static void nohz_balancer_kick(struct rq *rq) } } + sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu)); + if (sd) { + if (check_misfit_status(rq, sd)) { + flags = NOHZ_KICK_MASK; + goto unlock; + } + } + sd = rcu_dereference(per_cpu(sd_asym_packing, cpu)); if (sd) { for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) { -- 2.20.1