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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 52813C433E0 for ; Thu, 7 Jan 2021 11:27:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1E2223333 for ; Thu, 7 Jan 2021 11:27:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727803AbhAGL1h (ORCPT ); Thu, 7 Jan 2021 06:27:37 -0500 Received: from foss.arm.com ([217.140.110.172]:58372 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726151AbhAGL1g (ORCPT ); Thu, 7 Jan 2021 06:27:36 -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 AC92CED1; Thu, 7 Jan 2021 03:26:50 -0800 (PST) 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 41B833F719; Thu, 7 Jan 2021 03:26:49 -0800 (PST) From: Valentin Schneider To: Vincent Guittot , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org Cc: Vincent Guittot Subject: Re: [PATCH 3/3 v2] sched/fair: reduce cases for active balance In-Reply-To: <20210107103325.30851-4-vincent.guittot@linaro.org> References: <20210107103325.30851-1-vincent.guittot@linaro.org> <20210107103325.30851-4-vincent.guittot@linaro.org> User-Agent: Notmuch/0.21 (http://notmuchmail.org) Emacs/26.3 (x86_64-pc-linux-gnu) Date: Thu, 07 Jan 2021 11:26:47 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/01/21 11:33, Vincent Guittot wrote: > Active balance is triggered for a number of voluntary cases like misfit > or pinned tasks cases but also after that a number of load balance > attempts failed to migrate a task. There is no need to use active load > balance when the group is overloaded because an overloaded state means > that there is at least one waiting task. Nevertheless, the waiting task > is not selected and detached until the threshold becomes higher than its > load. This threshold increases with the number of failed lb (see the > condition if ((load >> env->sd->nr_balance_failed) > env->imbalance) in > detach_tasks()) and the waiting task will end up to be selected after a > number of attempts. > > Signed-off-by: Vincent Guittot > --- > kernel/sched/fair.c | 45 +++++++++++++++++++++++---------------------- > 1 file changed, 23 insertions(+), 22 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index a3515dea1afc..00ec5b901188 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -9499,13 +9499,32 @@ asym_active_balance(struct lb_env *env) > } > > static inline bool > -voluntary_active_balance(struct lb_env *env) > +imbalanced_active_balance(struct lb_env *env) > +{ > + struct sched_domain *sd = env->sd; > + > + /* > + * The imbalanced case includes the case of pinned tasks preventing a fair > + * distribution of the load on the system but also the even distribution of the > + * threads on a system with spare capacity > + */ Do you mean s/imbalanced/migrate_task/? This part here will affect group_imbalanced, group_asym_packing, and some others. > + if ((env->migration_type == migrate_task) && > + (sd->nr_balance_failed > sd->cache_nice_tries+2)) > + return 1; > + > + return 0; > +} > +