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 EF214C4363D for ; Wed, 23 Sep 2020 14:43:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B608321D43 for ; Wed, 23 Sep 2020 14:43:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726693AbgIWOnt (ORCPT ); Wed, 23 Sep 2020 10:43:49 -0400 Received: from foss.arm.com ([217.140.110.172]:47944 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbgIWOnt (ORCPT ); Wed, 23 Sep 2020 10:43:49 -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 9AF7E11D4; Wed, 23 Sep 2020 07:43:48 -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 3072E3F73B; Wed, 23 Sep 2020 07:43:47 -0700 (PDT) References: <20200921072424.14813-1-vincent.guittot@linaro.org> <20200921072424.14813-3-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 2/4 v2] sched/fair: reduce minimal imbalance threshold In-reply-to: <20200921072424.14813-3-vincent.guittot@linaro.org> Date: Wed, 23 Sep 2020 15:43:45 +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: > The 25% default imbalance threshold for DIE and NUMA domain is large > enough to generate significant unfairness between threads. A typical > example is the case of 11 threads running on 2x4 CPUs. The imbalance of > 20% between the 2 groups of 4 cores is just low enough to not trigger > the load balance between the 2 groups. We will have always the same 6 > threads on one group of 4 CPUs and the other 5 threads on the other > group of CPUS. With a fair time sharing in each group, we ends up with > +20% running time for the group of 5 threads. > > Consider decreasing the imbalance threshold for overloaded case where we > use the load to balance task and to ensure fair time sharing. > > Acked-by: Hillf Danton > Reviewed-by: Phil Auld > Signed-off-by: Vincent Guittot Reviewed-by: Valentin Schneider