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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 7BD17C33C8C for ; Tue, 7 Jan 2020 12:30:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CB1C2072A for ; Tue, 7 Jan 2020 12:30:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Lu63eo78" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727944AbgAGMaA (ORCPT ); Tue, 7 Jan 2020 07:30:00 -0500 Received: from merlin.infradead.org ([205.233.59.134]:50072 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726937AbgAGM37 (ORCPT ); Tue, 7 Jan 2020 07:29:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=IWIyXi1gVFEl0mksTr1DghHX8bjTId6K8sb/e1hCsoI=; b=Lu63eo78KESL7seVds7fAyKJU nlnGG6LCkIvdUqHTKiAhrR9RCnOqOvH+xAtR3788pxZOW2kPyIXRpRYYlfkLWJSQH1lUg3SW1qmiD SAsdb+SlfsvRg+8f9eYqw3PjBBn/BCGwIAA/NP3ub43a8YbyEuXXECkis77vD8lH10q92+5cXG5Zr piAN/YWa/i9y63EE74bS1wEtyt+4XCNJi7YJYJscf11lTUQUosDE9/s+RzNJxrdOwCDImAB34YTcW VKZRXYDKWF60DvfjKGiHDAfnWbm7Fv47W9YIMnbHSZppZySMgSVy575Em6c1gqEP+S8plC/D6UAK5 tZ4EnShVw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1ionzW-0006QS-EV; Tue, 07 Jan 2020 12:29:46 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0742A300693; Tue, 7 Jan 2020 13:28:11 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8FA8A2B48237D; Tue, 7 Jan 2020 13:29:43 +0100 (CET) Date: Tue, 7 Jan 2020 13:29:43 +0100 From: Peter Zijlstra To: Mel Gorman Cc: Vincent Guittot , Ingo Molnar , Phil Auld , 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 degree of load imbalance between SD_NUMA domains v2 Message-ID: <20200107122943.GW2827@hirez.programming.kicks-ass.net> References: <20191220084252.GL3178@techsingularity.net> <20200103143051.GA3027@techsingularity.net> <20200106145225.GB3466@techsingularity.net> <20200107095655.GF3466@techsingularity.net> <20200107112255.GV2827@hirez.programming.kicks-ass.net> <20200107114211.GH3466@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200107114211.GH3466@techsingularity.net> 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 Tue, Jan 07, 2020 at 11:42:11AM +0000, Mel Gorman wrote: > On Tue, Jan 07, 2020 at 12:22:55PM +0100, Peter Zijlstra wrote: > > > + /* Consider allowing a small imbalance between NUMA groups */ > > > + if (env->sd->flags & SD_NUMA) { > > > + struct sched_domain *child = env->sd->child; > > > > This assumes sd-child exists, which should be true for NUMA domains I > > suppose. > > > > I would be stunned if it was not. What sort of NUMA domain would not have > child domains? Does a memory-only NUMA node with no CPUs even generate > a scheduler domain? If it does, then I guess the check is necessary. I think it's fine, it was just my paranoia triggering. At the very least we'll have the single CPU domain there.