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,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 33915C169C4 for ; Mon, 11 Feb 2019 18:00:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0822E21B18 for ; Mon, 11 Feb 2019 18:00:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732441AbfBKSAR (ORCPT ); Mon, 11 Feb 2019 13:00:17 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:55126 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730124AbfBKSAR (ORCPT ); Mon, 11 Feb 2019 13:00:17 -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 16940EBD; Mon, 11 Feb 2019 10:00:17 -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 B4BFA3F675; Mon, 11 Feb 2019 10:00:15 -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 v2 1/3] sched/fair: Comment some nohz_balancer_kick() kick conditions Date: Mon, 11 Feb 2019 17:59:44 +0000 Message-Id: <20190211175946.4961-2-valentin.schneider@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190211175946.4961-1-valentin.schneider@arm.com> References: <20190211175946.4961-1-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 We now have a comment explaining the first sched_domain based NOHZ kick, so might as well comment them all. While at it, unwrap a line that fits under 80 characters. Co-authored-by: Peter Zijlstra Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 17fcd15400e1..0f32e9830ec3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9612,8 +9612,12 @@ static noinline void nohz_balancer_kick(struct rq *rq) sd = rcu_dereference(rq->sd); if (sd) { - if ((rq->cfs.h_nr_running >= 1) && - check_cpu_capacity(rq, sd)) { + /* + * If there's a CFS task and the current CPU has reduced + * capacity; kick the ILB to see if there's a better CPU to run + * on. + */ + if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) { flags = NOHZ_KICK_MASK; goto unlock; } @@ -9621,6 +9625,11 @@ static noinline void nohz_balancer_kick(struct rq *rq) sd = rcu_dereference(per_cpu(sd_asym_packing, cpu)); if (sd) { + /* + * When ASYM_PACKING; see if there's a more preferred CPU + * currently idle; in which case, kick the ILB to move tasks + * around. + */ for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) { if (sched_asym_prefer(i, cpu)) { flags = NOHZ_KICK_MASK; -- 2.20.1