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 93ADBC33C8C for ; Tue, 7 Jan 2020 12:28:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5926B2072A for ; Tue, 7 Jan 2020 12:28:29 +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="AqSeVqV+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727939AbgAGM22 (ORCPT ); Tue, 7 Jan 2020 07:28:28 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:47802 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726937AbgAGM21 (ORCPT ); Tue, 7 Jan 2020 07:28:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=512YgnwE6XKHmE+IOxEt/LFAOvuO2Sym2koW+nQjqUA=; b=AqSeVqV+0danT1jt89bzLqI2W Gg1kOMA5dHT8gtgbaotRM8sBU9Zl8La7ZHBQO0SYWOISYZdE81G8ULwgaCI728pEOlGxx8sezlm7E 4UceAcKy5XPHTIieGAFZPIVFXASVmr6XJofGtjI/rfemw9BAE0rEoUtaPqoEPGqCpDvSdeL6sKXdn 802lRP4Ib7OLEb+FTy+7R3nUWLmHpU7UCRbo7G3/8WiVUM2mPMRZegmJFisK6OgfPACYrhziYr+iy jVmJ4voJGEdU79m8HGGC2yywjrR2dP0HAPzo1+M7wRWKuCfM9/+djuhPC3EQYJbfxQ0Jen+vX7+dI k4Pehk4tg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iony0-0004OS-5Y; Tue, 07 Jan 2020 12:28:12 +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 9A2143012C3; Tue, 7 Jan 2020 13:26:36 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 27D782B26EAB9; Tue, 7 Jan 2020 13:28:09 +0100 (CET) Date: Tue, 7 Jan 2020 13:28:09 +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: <20200107122809.GU2871@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200107112255.GV2827@hirez.programming.kicks-ass.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 12:22:55PM +0100, Peter Zijlstra wrote: > On Tue, Jan 07, 2020 at 09:56:55AM +0000, Mel Gorman wrote: > > + unsigned int imbalance_adj; > > + > > + /* > > + * Calculate an acceptable degree of imbalance based > > + * on imbalance_adj. However, do not allow a greater > > + * imbalance than the child domains weight to avoid > > + * a case where the allowed imbalance spans multiple > > + * LLCs. > > + */ > > That comment is a wee misleading, @child is not an LLC per se. This > could be the NUMA distance 2 domain, in which case @child is the NUMA > distance 1 group. > > That said, even then it probably makes sense to ensure you don't idle a > whole smaller distance group. Hmm, one more thing. On AMD EPYC, which the multiple LLCs, you'll have the single NODE domain in between, and that is not marked with SD_NUMA (iirc). So specifically the case you want to handle is not in fact handled. The first SD_NUMA (distance-1) will have all NODE children, which on EPYC are not LLCs.