From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753709Ab0DSSPG (ORCPT ); Mon, 19 Apr 2010 14:15:06 -0400 Received: from gir.skynet.ie ([193.1.99.77]:58085 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752929Ab0DSSPE (ORCPT ); Mon, 19 Apr 2010 14:15:04 -0400 Date: Mon, 19 Apr 2010 19:14:42 +0100 From: Mel Gorman To: KAMEZAWA Hiroyuki Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, "linux-mm@kvack.org" , "minchan.kim@gmail.com" , "kosaki.motohiro@jp.fujitsu.com" Subject: Re: error at compaction (Re: mmotm 2010-04-15-14-42 uploaded Message-ID: <20100419181442.GA19264@csn.ul.ie> References: <201004152210.o3FMA7KV001909@imap1.linux-foundation.org> <20100419190133.50a13021.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100419190133.50a13021.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 19, 2010 at 07:01:33PM +0900, KAMEZAWA Hiroyuki wrote: > > mmotm 2010-04-15-14-42 > > When I tried > # echo 0 > /proc/sys/vm/compaction > > I see following. > > My enviroment was > 2.6.34-rc4-mm1+ (2010-04-15-14-42) (x86-64) CPUx8 > allocating tons of hugepages and reduce free memory. > > What I did was: > # echo 0 > /proc/sys/vm/compact_memory > > Hmm, I see this kind of error at migation for the 1st time.. > my.config is attached. Hmm... ? > > (I'm sorry I'll be offline soon.) That's ok, thanks you for the report. I'm afraid I made little progress as I spent most of the day on other bugs but I do have something for you. First, I reproduced the problem using your .config. However, the problem does not manifest with the .config I normally use which is derived from the distro kernel configuration (Debian Lenny). So, there is something in your .config that triggers the problem. I very strongly suspect this is an interaction between migration, compaction and page allocation debug. Compaction takes pages directly off the buddy list and I bet you a shiny penny they are still unmapped when the copy takes place resulting in your oops. I'll verify the theory tomorrow but it's a plausible explanation. On a different note, where did config options like the following come out of? CONFIG_ARCH_HWEIGHT_CFLAGS="-fcall-saved-rdi -fcall-saved-rsi -fcall-saved-rdx -fcall-saved-rcx -fcall-saved-r8 -fcall-saved-r9 -fcall-saved-r10 -fcall-saved-r11" I don't think they are a factor but I'm curious. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab