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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 0CB6EC33CB1 for ; Fri, 17 Jan 2020 14:15:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDF622082F for ; Fri, 17 Jan 2020 14:15:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728827AbgAQOPH (ORCPT ); Fri, 17 Jan 2020 09:15:07 -0500 Received: from outbound-smtp23.blacknight.com ([81.17.249.191]:50825 "EHLO outbound-smtp23.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726587AbgAQOPH (ORCPT ); Fri, 17 Jan 2020 09:15:07 -0500 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp23.blacknight.com (Postfix) with ESMTPS id C8240B8BC3 for ; Fri, 17 Jan 2020 14:15:05 +0000 (GMT) Received: (qmail 8437 invoked from network); 17 Jan 2020 14:15:05 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.18.57]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 17 Jan 2020 14:15:05 -0000 Date: Fri, 17 Jan 2020 14:15:03 +0000 From: Mel Gorman To: Vincent Guittot Cc: Phil Auld , Ingo Molnar , Peter Zijlstra , Valentin Schneider , Srikar Dronamraju , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Hillf Danton , Parth Shah , Rik van Riel , LKML Subject: Re: [PATCH] sched, fair: Allow a small load imbalance between low utilisation SD_NUMA domains v4 Message-ID: <20200117141503.GQ3466@techsingularity.net> References: <20200114101319.GO3466@techsingularity.net> <20200116163529.GP3466@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: 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, Jan 17, 2020 at 02:08:13PM +0100, Vincent Guittot wrote: > > > This patch allows a fixed degree of imbalance of two tasks to exist > > > between NUMA domains regardless of utilisation levels. In many cases, > > > this prevents communicating tasks being pulled apart. It was evaluated > > > whether the imbalance should be scaled to the domain size. However, no > > > additional benefit was measured across a range of workloads and machines > > > and scaling adds the risk that lower domains have to be rebalanced. While > > > this could change again in the future, such a change should specify the > > > use case and benefit. > > > > > > > Any thoughts on whether this is ok for tip or are there suggestions on > > an alternative approach? > > I have just finished to run some tests on my system with your patch > and I haven't seen any noticeable any changes so far which was a bit > expected. The tests that I usually run, use more than 4 tasks on my 2 > nodes system; This is indeed expected. With more active tasks, normal load balancing applies. > the only exception is perf sched pipe and the results > for this test stays the same with and without your patch. I never saw much difference with perf sched pipe either. It was generally within the noise. > I'm curious > if this impacts Phil's tests which run LU.c benchmark with some > burning cpu tasks I didn't see any problem with LU.c whether parallelised by openMPI or openMP but an independent check would be nice. -- Mel Gorman SUSE Labs