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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 9FFBAC43141 for ; Thu, 14 Nov 2019 16:23:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83BE5206DA for ; Thu, 14 Nov 2019 16:23:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726786AbfKNQXj (ORCPT ); Thu, 14 Nov 2019 11:23:39 -0500 Received: from foss.arm.com ([217.140.110.172]:45768 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726263AbfKNQXj (ORCPT ); Thu, 14 Nov 2019 11:23:39 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 486E9328; Thu, 14 Nov 2019 08:23:38 -0800 (PST) Received: from [192.168.1.15] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0134C3F52E; Thu, 14 Nov 2019 08:23:34 -0800 (PST) Subject: Re: [PATCH v3] sched/freq: move call to cpufreq_update_util To: Vincent Guittot , linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, rostedt@goodmis.org, mgorman@suse.de, dsmythies@telus.net Cc: linux-pm@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, sargun@sargun.me, tj@kernel.org, xiexiuqi@huawei.com, xiezhipeng1@huawei.com, srinivas.pandruvada@linux.intel.com References: <1573676461-7990-1-git-send-email-vincent.guittot@linaro.org> From: Dietmar Eggemann Message-ID: <5a56358b-83f5-09db-17f0-dbdeecba2ff3@arm.com> Date: Thu, 14 Nov 2019 17:23:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <1573676461-7990-1-git-send-email-vincent.guittot@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13.11.19 21:21, Vincent Guittot wrote: > update_cfs_rq_load_avg() calls cfs_rq_util_change() everytime pelt decays, > which might be inefficient when cpufreq driver has rate limitation. > > When a task is attached on a CPU, we have call path: > > update_load_avg() > update_cfs_rq_load_avg() > cfs_rq_util_change -- > trig frequency update > attach_entity_load_avg() > cfs_rq_util_change -- > trig frequency update > > The 1st frequency update will not take into account the utilization of the > newly attached task and the 2nd one might be discard because of rate > limitation of the cpufreq driver. > > update_cfs_rq_load_avg() is only called by update_blocked_averages() > and update_load_avg() so we can move the call to > cfs_rq_util_change/cpufreq_update_util() into these 2 functions. It's also > interesting to notice that update_load_avg() already calls directly > cfs_rq_util_change() for !SMP case. > > This changes will also ensure that cpufreq_update_util() is called even > when there is no more CFS rq in the leaf_cfs_rq_list to update but only > irq, rt or dl pelt signals. > > Reported-by: Doug Smythies > Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path") > Signed-off-by: Vincent Guittot Reviewed-by: Dietmar Eggemann > --- > > changes for v3: > - fix typo > - test the decay of root cfs_rq even for !CONFIG_FAIR_GROUP_SCHED case nit: s/!CONFIG_FAIR_GROUP_SCHED/CONFIG_FAIR_GROUP_SCHED [...] > @@ -7543,6 +7544,7 @@ static void update_blocked_averages(int cpu) > const struct sched_class *curr_class; > struct rq_flags rf; > bool done = true; > + int decayed; > > rq_lock_irqsave(rq, &rf); > update_rq_clock(rq); > @@ -7552,9 +7554,9 @@ static void update_blocked_averages(int cpu) > * that RT, DL and IRQ signals have been updated before updating CFS. > */ tip/sched/urgent's b90f7c9d2198 ("sched/pelt: Fix update of blocked PELT ordering") adds this comment to both update_blocked_averages() implementations. It mentions explicitly that update_cfs_rq_load_avg() can call cpufreq_update_util(). Something this patch changes. Might be good to update the comments with this patch as well. [...]