Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751957Ab0HXLyK (ORCPT ); Tue, 24 Aug 2010 07:54:10 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:42497 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751607Ab0HXLyF convert rfc822-to-8bit (ORCPT ); Tue, 24 Aug 2010 07:54:05 -0400 Subject: Re: [PATCH 0/4] Finer granularity and task/cgroup irq time accounting From: Peter Zijlstra To: balbir@linux.vnet.ibm.com Cc: Venkatesh Pallipadi , Martin Schwidefsky , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Paul Menage , linux-kernel@vger.kernel.org, Paul Turner , Heiko Carstens , Paul Mackerras , Tony Luck In-Reply-To: <20100824113801.GO4684@balbir.in.ibm.com> References: <1279583835-22854-1-git-send-email-venki@google.com> <20100720095546.2f899e04@mschwide.boeblingen.de.ibm.com> <20100722131239.208d9501@mschwide.boeblingen.de.ibm.com> <1282636286.2605.2307.camel@laptop> <20100824080515.GK4684@balbir.in.ibm.com> <1282640953.2605.2428.camel@laptop> <20100824113801.GO4684@balbir.in.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Tue, 24 Aug 2010 13:53:55 +0200 Message-ID: <1282650835.2605.2629.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 961 Lines: 23 On Tue, 2010-08-24 at 17:08 +0530, Balbir Singh wrote: > > The point is for containers it is more likely to give the right answer > and so on. Yes, the results are not 100% accurate. Consider one group heavily dirtying pages, it stuffs the IO queues full and gets blocked on IO completion. Since the CPU is then free to schedule something else we start running things from another group, those IO completions will come in while we run other group and get accounted to other group -- FAIL. s/group/task/ etc.. That just really doesn't work, accounting async work, esp stuff that is not under software control it very tricky indeed. So what are you wanting to do, and why. Do you really need accounting madness? -- 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/