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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 241E5C004D3 for ; Mon, 22 Oct 2018 22:22:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18A3D20652 for ; Mon, 22 Oct 2018 22:22:58 +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="q96QQ2L5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18A3D20652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729084AbeJWGnU (ORCPT ); Tue, 23 Oct 2018 02:43:20 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:33472 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726800AbeJWGnU (ORCPT ); Tue, 23 Oct 2018 02:43:20 -0400 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=0exL65SMWkt7bA7UoCUM+yr7wNAAQcfagAceHNam41U=; b=q96QQ2L5bUuG9AD7rVYRQHwi+ sDSgEpRdf7Q3T+0WqVRNrH/tJ2gqXeCR2sbuUV9nItNfRjBSh1eosggVVVKJYQ97bTwuiXSxBzLfY bCiNXowg2RpQ/ZboGVLH/NWdpZrpAlJ8O12ZaqYfjA65lETvwjvbsPwEYjCvhw/ZHSsYxZ0E6Fof/ uk1ZwMEZbo8QE+Fapa6AYOnTmsZBOeQD+oM6xnJsoKx+okp3/Qo4ygdP933aBEE9wgrewCZNNeDUW BIA3WLTtPahZHPmpMJgBLHa9cEB95+Kj+VoUd1+Ou9jdt8EiYk0SChGMtdp6YhLeOz2umsiVLo1tj pUpu3B5GQ==; Received: from [167.98.65.38] (helo=worktop) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gEib3-0000Kr-LT; Mon, 22 Oct 2018 22:22:49 +0000 Received: by worktop (Postfix, from userid 1000) id 323306E08B3; Tue, 23 Oct 2018 00:05:09 +0200 (CEST) Date: Tue, 23 Oct 2018 00:05:09 +0200 From: Peter Zijlstra To: Steven Sistare Cc: mingo@redhat.com, subhra.mazumdar@oracle.com, dhaval.giani@oracle.com, rohit.k.jain@oracle.com, daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com, matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com, riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com Subject: Re: [PATCH 09/10] sched/fair: disable stealing if too many NUMA nodes Message-ID: <20181022220509.GC3109@worktop.c.hoisthospitality.com> References: <1540220381-424433-1-git-send-email-steven.sistare@oracle.com> <1540220381-424433-10-git-send-email-steven.sistare@oracle.com> <20181022170604.GG3117@worktop.programming.kicks-ass.net> <1356a3cc-a9f2-6593-4737-1b20fc5daa75@oracle.com> <274b79fd-b001-3d30-3773-7f01940ca8a6@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <274b79fd-b001-3d30-3773-7f01940ca8a6@oracle.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 22, 2018 at 03:21:20PM -0400, Steven Sistare wrote: > On 10/22/2018 2:47 PM, Steven Sistare wrote: > > On 10/22/2018 1:06 PM, Peter Zijlstra wrote: > >> On Mon, Oct 22, 2018 at 07:59:40AM -0700, Steve Sistare wrote: > >>> The STEAL feature causes regressions on hackbench on larger NUMA systems, > >>> so disable it on systems with more than sched_steal_node_limit nodes > >>> (default 2). > >> > >> How come? From a quick read the stealing is per LLC, where do we steal > >> across nodes? > > > > See the complete explanation in this patch. It is deeper than can be gleaned > > from a quick read. > > I should have said a bit more. Your quick take on stealing is correct, we do > not steal across nodes. However, stealing reduces average run queue length which > influences wake_affine migrations. Now see the complete explanation. Right; read a bit more just now. hackbench is a fairly poor benchmark for numa performance. One that comes to mind is multi wharehouse specjbb stuff (assuming you have numa balance enabled of course).