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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D2ED5C433E2 for ; Tue, 15 Sep 2020 19:12:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95BA020771 for ; Tue, 15 Sep 2020 19:12:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728050AbgIOTMO (ORCPT ); Tue, 15 Sep 2020 15:12:14 -0400 Received: from foss.arm.com ([217.140.110.172]:42242 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727961AbgIOTFB (ORCPT ); Tue, 15 Sep 2020 15:05:01 -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 7BF3311D4; Tue, 15 Sep 2020 12:04:59 -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 457223F718; Tue, 15 Sep 2020 12:04:58 -0700 (PDT) References: <20200914100340.17608-1-vincent.guittot@linaro.org> <20200914100340.17608-5-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 Subject: Re: [PATCH 4/4] sched/fair: reduce busy load balance interval In-reply-to: <20200914100340.17608-5-vincent.guittot@linaro.org> Date: Tue, 15 Sep 2020 20:04:56 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/09/20 11:03, Vincent Guittot wrote: > The busy_factor, which increases load balance interval when a cpu is busy, > is set to 32 by default. This value generates some huge LB interval on > large system like the THX2 made of 2 node x 28 cores x 4 threads. > For such system, the interval increases from 112ms to 3584ms at MC level. > And from 228ms to 7168ms at NUMA level. > > Even on smaller system, a lower busy factor has shown improvement on the > fair distribution of the running time so let reduce it for all. > ISTR you mentioned taking this one step further and making (interval * busy_factor) scale logarithmically with the number of CPUs to avoid reaching outrageous numbers. Did you experiment with that already? > Signed-off-by: Vincent Guittot > --- > kernel/sched/topology.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 1a84b778755d..a8477c9e8569 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -1336,7 +1336,7 @@ sd_init(struct sched_domain_topology_level *tl, > *sd = (struct sched_domain){ > .min_interval = sd_weight, > .max_interval = 2*sd_weight, > - .busy_factor = 32, > + .busy_factor = 16, > .imbalance_pct = 117, > > .cache_nice_tries = 0,