Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755883Ab0KNBPR (ORCPT ); Sat, 13 Nov 2010 20:15:17 -0500 Received: from mail-vw0-f46.google.com ([209.85.212.46]:64653 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753080Ab0KNBPM convert rfc822-to-8bit (ORCPT ); Sat, 13 Nov 2010 20:15:12 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=YNkDAknR3xCql2HZCaKnJD+Z5Clzq0hfJoGacoXX19ERq4CWkYk3cPCRkGUuHSYJtu MW8Vqh0+EBh5LwsNhntXkO8mbEfoWau5MG2G4hxzTQkTigTbls9lXd5d/9HndZbZ+q7Z cWhHVkgFp3mHnVD452xoXO/rmV9qNV/uqOuqc= MIME-Version: 1.0 In-Reply-To: <1289500084.2698.12.camel@zim> References: <20101104041236.GA9389@helgaas.com> <1288847992.2718.37.camel@edumazet-laptop> <20101104142853.GA11656@helgaas.com> <1288881474.2659.123.camel@edumazet-laptop> <20101105020013.GA13484@helgaas.com> <1288937844.3234.1.camel@edumazet-laptop> <1289500084.2698.12.camel@zim> Date: Sat, 13 Nov 2010 17:15:10 -0800 X-Google-Sender-Auth: o0eNSTVYAPUFgZCYD4vOawsGdbc Message-ID: Subject: Re: divide error in select_task_rq_fair() From: Yinghai Lu To: Myron Stowe Cc: Eric Dumazet , Bjorn Helgaas , Ingo Molnar , Peter Zijlstra , Venkatesh Pallipadi , Nikhil Rao , Takuya Yoshikawa , linux-kernel@vger.kernel.org, knikanth@suse.de, rjenties@google.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2715 Lines: 65 On Thu, Nov 11, 2010 at 10:28 AM, Myron Stowe wrote: > On Fri, 2010-11-05 at 07:17 +0100, Eric Dumazet wrote: >> Le jeudi 04 novembre 2010 ? 20:00 -0600, Bjorn Helgaas a ?crit : >> >> > Is that going to help you debug the problem? ?The solution is not going >> > to be something like "set NR_CPUS=x". ?If NR_CPUS is too small, the >> > machine should still *boot*, even if we can't use all the CPUs in the >> > box. >> > >> >> Yes, it will help to understand the layout of cpu / domains and make >> appropriate changes. >> >> Alternative is you send me such a machine :=) > > I opened a BZ on this issue as it seems to be a regression - > https://bugzilla.kernel.org/show_bug.cgi?id=22662 > > I also, as indicated in the BZ, bisected the kernel which gave the > following results and reverting 50f2d7f682f9c0ed58191d0982fe77888d59d162 > did re-enable booting on the box in question (an HP dl980g7). ?Let me > know what further info you need or patches to test for debugging this. > > Thanks, > > commit 50f2d7f682f9c0ed58191d0982fe77888d59d162 > Author: Nikanth Karthikesan > Date: ? Thu Sep 30 17:34:10 2010 +0530 > > ? ?x86, numa: Assign CPUs to nodes in round-robin manner on fake NUMA > > ? ?commit d9c2d5ac6af87b4491bff107113aaf16f6c2b2d9 "x86, numa: Use near(er) > ? ?online node instead of roundrobin for NUMA" changed NUMA initialization on > ? ?Intel to choose the nearest online node or first node. ?Fake NUMA would be > ? ?better of with round-robin initialization, instead of the all CPUS on > ? ?first node. ?Change the choice of first node, back to round-robin. > > ? ?For testing NUMA kernel behaviour without cpusets and NUMA aware > ? ?applications, it would be better to have cpus in different nodes, rather > ? ?than all in a single node. ?With cpusets migration of tasks scenarios > ? ?cannot not be tested. > > ? ?I guess having it round-robin shouldn't affect the use cases for all cpus > ? ?on the first node. > > ? ?The code comments in arch/x86/mm/numa_64.c:759 indicate that this used to > ? ?be the case, which was changed by commit d9c2d5ac6. ?It changed from > ? ?roundrobin to nearer or first node. ?And I couldn't find any reason for > ? ?this change in its changelog. > > ? ?Signed-off-by: Nikanth Karthikesan > ? ?Cc: David Rientjes > ? ?Signed-off-by: Andrew Morton please check http://lkml.org/lkml/2010/11/13/176 Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/