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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 3A7F1C4363D for ; Wed, 23 Sep 2020 14:43:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ECCAF206FB for ; Wed, 23 Sep 2020 14:43:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726670AbgIWOnn (ORCPT ); Wed, 23 Sep 2020 10:43:43 -0400 Received: from foss.arm.com ([217.140.110.172]:47924 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbgIWOnn (ORCPT ); Wed, 23 Sep 2020 10:43:43 -0400 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 08860113E; Wed, 23 Sep 2020 07:43:43 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 90BA93F73B; Wed, 23 Sep 2020 07:43:41 -0700 (PDT) References: <20200921072424.14813-1-vincent.guittot@linaro.org> <20200921072424.14813-2-vincent.guittot@linaro.org> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Vincent Guittot Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org, pauld@redhat.com, hdanton@sina.com Subject: Re: [PATCH 1/4 v2] sched/fair: relax constraint on task's load during load balance In-reply-to: <20200921072424.14813-2-vincent.guittot@linaro.org> Date: Wed, 23 Sep 2020 15:43:19 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/09/20 08:24, Vincent Guittot wrote: > Some UCs like 9 always running tasks on 8 CPUs can't be balanced and the > load balancer currently migrates the waiting task between the CPUs in an > almost random manner. The success of a rq pulling a task depends of the > value of nr_balance_failed of its domains and its ability to be faster > than others to detach it. This behavior results in an unfair distribution > of the running time between tasks because some CPUs will run most of the > time, if not always, the same task whereas others will share their time > between several tasks. > > Instead of using nr_balance_failed as a boolean to relax the condition > for detaching task, the LB will use nr_balanced_failed to relax the > threshold between the tasks'load and the imbalance. This mecanism > prevents the same rq or domain to always win the load balance fight. > > Reviewed-by: Phil Auld > Signed-off-by: Vincent Guittot Reviewed-by: Valentin Schneider