Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934773Ab0GOUuR (ORCPT ); Thu, 15 Jul 2010 16:50:17 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:43836 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934733Ab0GOUuN (ORCPT ); Thu, 15 Jul 2010 16:50:13 -0400 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; b=FJcB7HY3EDECjhR871r5oXWVN9uc03CV5oE20Rv/GURz84OYqJoUoAnSr1GyA57pKs WJzcefs0js/jHAhBnbcPgRAgfUyphXaEGH7rbKqnzoQQAUmmAUNSlJ5uG7NuqeW+bI6Y b9gYPXzdCCcE3xP6FTx0omWIN6ATfV9jX6S/o= MIME-Version: 1.0 In-Reply-To: References: <1279100846.8592.53.camel@e102109-lin.cambridge.arm.com> <4C3D89AC.4040303@cs.helsinki.fi> <1279205891.6664.46.camel@e102109-lin.cambridge.arm.com> <4C3F2F52.2050101@cs.helsinki.fi> <20100715162805.GA10240@brouette> <20100715191638.GA3694@brouette> <20100715200012.GA4175@brouette> Date: Thu, 15 Jul 2010 23:50:09 +0300 X-Google-Sender-Auth: yDGueKr3eXa4A96PjUkmm599zUo Message-ID: Subject: Re: kmemleak, cpu usage jump out of nowhere From: Pekka Enberg To: Zeno Davatz Cc: Damien Wyart , Catalin Marinas , "linux-kernel@vger.kernel.org" , Andrew Morton , "x86@kernel.org" , "mingo@elte.hu" , "yinghai@kernel.org" , Peter Zijlstra Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3145 Lines: 72 On Thu, Jul 15, 2010 at 11:38 PM, Zeno Davatz wrote: > Am 15.07.2010 um 22:00 schrieb Damien Wyart : > >>>> For now, I can't reproduce the problem with CONFIG_NO_BOOTMEM disabled ; >>>> with the option and rc5 the problem was happening quite quickly after >>>> boot and normal use of the machine. So it seems I can confirme what Zeno >>>> has seen and I hope this will give a hint to debug the problem. I guess >>>> this has not been reported that much because many testers might not have >>>> enabled CONFIG_NO_BOOTMEM... Maybe the scheduler folks could test their >>>> benchmark with a kernel having this option enabled? >> >> * Pekka Enberg [2010-07-15 22:50]: >>> To be honest, the bug is bit odd. It's related to boot-time memory >>> allocator changes but yet it seems to manifest itself as a scheduling >>> problem. So if you have some spare time and want to speed up the >>> debugging process, please test v2.6.34 and v2.6.35-rc1 with >>> CONFIG_NO_BOOTMEM and if former is good and latter is bad, try to see >>> if you can identify the offending commit with "git bisect." >> >> Not sure I will have enough time in the coming days (doing that remotely >> is fishy since ssh access is almost stuck when the problem occurs); if >> Zeno can and would like to do it, maybe this could be done faster. >> >> As the scheduler is now very well instrumented (many debugging features >> are available), reproducing the bug on a test platform (it happens quite >> quickly for me) might also give some hints. So testers, if you have >> time, please test 2.6.35-rc5 with CONFIG_NO_BOOTMEM on a Core i7 and see >> if you can reproduce the problem! > > Will try to do so. Can you point me to the git bisect howto with the versions you want. Cool. So like I said, you first want to test 2.6.34 to find a known good version. Please remember to make sure you have CONFIG_NO_BOOTMEM enabled. You can also try to speed up the process by testing 2.6.35-rc1 which is likely to include the offending commit. That's not strictly necessary as long as you are sure that you have some 2.6.35-rc kernel that's bad. After that, bisecting is as simple as: git bisect start git bisect good v2.6.34 git bisect bad v2.6.31-rc1 # or some other kernel you know to be bad then git bisect bad # if you were able to trigger the problem or git bisect good # if the problem doesn't exist git will then find the next revision to test after which you do and repeat the "git bisect good/bad" step until git tells you it has found the offending commit. There's more information on the git bisect man pages: http://www.kernel.org/pub/software/scm/git/docs/git-bisect.html Let me know if you need more help with this. Pekka -- 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/