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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4F556C5DF60 for ; Fri, 8 Nov 2019 18:37:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B9222087E for ; Fri, 8 Nov 2019 18:37:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728852AbfKHShg (ORCPT ); Fri, 8 Nov 2019 13:37:36 -0500 Received: from outbound-smtp16.blacknight.com ([46.22.139.233]:59638 "EHLO outbound-smtp16.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726349AbfKHShg (ORCPT ); Fri, 8 Nov 2019 13:37:36 -0500 Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp16.blacknight.com (Postfix) with ESMTPS id 2D6A71C2E59 for ; Fri, 8 Nov 2019 18:37:33 +0000 (GMT) Received: (qmail 22085 invoked from network); 8 Nov 2019 18:37:33 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.23.195]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 8 Nov 2019 18:37:32 -0000 Date: Fri, 8 Nov 2019 18:37:30 +0000 From: Mel Gorman To: Vincent Guittot Cc: linux-kernel , Ingo Molnar , Peter Zijlstra , Phil Auld , Valentin Schneider , Srikar Dronamraju , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Hillf Danton , Parth Shah , Rik van Riel Subject: Re: [PATCH v4 04/11] sched/fair: rework load_balance Message-ID: <20191108183730.GU3016@techsingularity.net> References: <1571405198-27570-1-git-send-email-vincent.guittot@linaro.org> <1571405198-27570-5-git-send-email-vincent.guittot@linaro.org> <20191030154534.GJ3016@techsingularity.net> <20191031101544.GP3016@techsingularity.net> <20191031114020.GQ3016@techsingularity.net> <20191108163501.GA26528@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20191108163501.GA26528@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 08, 2019 at 05:35:01PM +0100, Vincent Guittot wrote: > > Fair enough, netperf hits the corner case where it does not work but > > that is also true without your series. > > I run mmtest/netperf test on my setup. It's a mix of small positive or > negative differences (see below) > > > > netperf-tcp > 5.3-rc2 5.3-rc2 > tip +rwk+fix > Hmean 64 871.30 ( 0.00%) 860.90 * -1.19%* > Hmean 128 1689.39 ( 0.00%) 1679.31 * -0.60%* > Hmean 256 3199.59 ( 0.00%) 3241.98 * 1.32%* > Hmean 1024 9390.47 ( 0.00%) 9268.47 * -1.30%* > Hmean 2048 13373.95 ( 0.00%) 13395.61 * 0.16%* > Hmean 3312 16701.30 ( 0.00%) 17165.96 * 2.78%* > Hmean 4096 15831.03 ( 0.00%) 15544.66 * -1.81%* > Hmean 8192 19720.01 ( 0.00%) 20188.60 * 2.38%* > Hmean 16384 23925.90 ( 0.00%) 23914.50 * -0.05%* > Stddev 64 7.38 ( 0.00%) 4.23 ( 42.67%) > Stddev 128 11.62 ( 0.00%) 10.13 ( 12.85%) > Stddev 256 34.33 ( 0.00%) 7.94 ( 76.88%) > Stddev 1024 35.61 ( 0.00%) 116.34 (-226.66%) > Stddev 2048 285.30 ( 0.00%) 80.50 ( 71.78%) > Stddev 3312 304.74 ( 0.00%) 449.08 ( -47.36%) > Stddev 4096 668.11 ( 0.00%) 569.30 ( 14.79%) > Stddev 8192 733.23 ( 0.00%) 944.38 ( -28.80%) > Stddev 16384 553.03 ( 0.00%) 299.44 ( 45.86%) > > 5.3-rc2 5.3-rc2 > tip +rwk+fix > Duration User 138.05 140.95 > Duration System 1210.60 1208.45 > Duration Elapsed 1352.86 1352.90 > This roughly matches what I've seen. The interesting part to me for netperf is the next section of the report that reports the locality of numa hints. With netperf on a 2-socket machine, it's generally around 50% as the client/server are pulled apart. Because netperf is not heavily memory bound, it doesn't have much impact on the overall performance but it's good at catching the cross-node migrations. > > > > > I agree that additional patches are probably needed to improve load > > > balance at NUMA level and I expect that this rework will make it > > > simpler to add. > > > I just wanted to get the output of some real use cases before defining > > > more numa level specific conditions. Some want to spread on there numa > > > nodes but other want to keep everything together. The preferred node > > > and fbq_classify_group was the only sensible metrics to me when he > > > wrote this patchset but changes can be added if they make sense. > > > > > > > That's fair. While it was possible to address the case before your > > series, it was a hatchet job. If the changelog simply notes that some > > special casing may still be required for SD_NUMA but it's outside the > > scope of the series, then I'd be happy. At least there is a good chance > > then if there is follow-up work that it won't be interpreted as an > > attempt to reintroduce hacky heuristics. > > > > Would the additional comment make sense for you about work to be done > for SD_NUMA ? > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 0ad4b21..7e4cb65 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6960,11 +6960,34 @@ enum fbq_type { regular, remote, all }; > * group. see update_sd_pick_busiest(). > */ > enum group_type { > + /* > + * The group has spare capacity that can be used to process more work. > + */ > group_has_spare = 0, > + /* > + * The group is fully used and the tasks don't compete for more CPU > + * cycles. Nevetheless, some tasks might wait before running. > + */ > group_fully_busy, > + /* > + * One task doesn't fit with CPU's capacity and must be migrated on a > + * more powerful CPU. > + */ > group_misfit_task, > + /* > + * One local CPU with higher capacity is available and task should be > + * migrated on it instead on current CPU. > + */ > group_asym_packing, > + /* > + * The tasks affinity prevents the scheduler to balance the load across > + * the system. > + */ > group_imbalanced, > + /* > + * The CPU is overloaded and can't provide expected CPU cycles to all > + * tasks. > + */ > group_overloaded > }; Looks good. > > @@ -8563,7 +8586,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s > > /* > * Try to use spare capacity of local group without overloading it or > - * emptying busiest > + * emptying busiest. > + * XXX Spreading tasks across numa nodes is not always the best policy > + * and special cares should be taken for SD_NUMA domain level before > + * spreading the tasks. For now, load_balance() fully relies on > + * NUMA_BALANCING and fbq_classify_group/rq to overide the decision. > */ > if (local->group_type == group_has_spare) { > if (busiest->group_type > group_fully_busy) { Perfect. Any patch in that are can then update the comment and it should be semi-obvious to the next reviewer that it's expected. Thanks Vincent. -- Mel Gorman SUSE Labs