From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1425737AbeBOQVj (ORCPT ); Thu, 15 Feb 2018 11:21:39 -0500 Received: from foss.arm.com ([217.140.101.70]:57122 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1425690AbeBOQVc (ORCPT ); Thu, 15 Feb 2018 11:21:32 -0500 From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: valentin.schneider@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, Morten Rasmussen Subject: [PATCH 5/7] sched/fair: Kick nohz balance if rq->misfit_task Date: Thu, 15 Feb 2018 16:20:52 +0000 Message-Id: <1518711654-23503-6-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1518711654-23503-1-git-send-email-morten.rasmussen@arm.com> References: <1518711654-23503-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Valentin Schneider There already are a few conditions in nohz_kick_needed() to ensure a nohz kick is triggered, but they are not enough for some misfit task scenarios. Excluding asym packing, those are: * rq->nr_running >=2: Not relevant here because we are running a misfit task, it needs to be migrated regardless and potentially through active balance. * sds->nr_busy_cpus > 1: If there is only the misfit task being run on a group of low capacity cpus, this will be evaluated to False. * rq->cfs.h_nr_running >=1 && check_cpu_capacity(): Not relevant here, misfit task needs to be migrated regardless of rt/IRQ pressure As such, this commit adds an rq->misfit_task condition to trigger a nohz kick. The idea to kick a nohz balance for misfit tasks originally came from Leo Yan , and a similar patch was submitted for the Android Common Kernel - see [1]. [1]: https://lists.linaro.org/pipermail/eas-dev/2016-September/000551.html cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Valentin Schneider Signed-off-by: Morten Rasmussen --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e036aef3f10a..1439b784b1f0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9411,6 +9411,9 @@ static inline bool nohz_kick_needed(struct rq *rq) if (rq->nr_running >= 2) return true; + if (rq->misfit_task_load) + return true; + rcu_read_lock(); sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) { -- 2.7.4