Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757263AbXJGWSX (ORCPT ); Sun, 7 Oct 2007 18:18:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753307AbXJGWSR (ORCPT ); Sun, 7 Oct 2007 18:18:17 -0400 Received: from tone.orchestra.cse.unsw.EDU.AU ([129.94.242.59]:41726 "EHLO tone.orchestra.cse.unsw.EDU.AU" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752232AbXJGWSQ (ORCPT ); Sun, 7 Oct 2007 18:18:16 -0400 X-Greylist: delayed 418 seconds by postgrey-1.27 at vger.kernel.org; Sun, 07 Oct 2007 18:18:15 EDT From: Joshua Root To: Ingo Molnar Date: Mon, 08 Oct 2007 08:10:47 +1000 X-Spam-Score: 0.35 X-CSE-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on tone.orchestra.cse.unsw.EDU.AU X-CSE-Spam-Level: X-CSE-Spam-Status: No, score=-2.6 required=4.0 tests=BAYES_00,UNPARSEABLE_RELAY autolearn=ham version=3.1.3 Message-ID: <47095967.8060608@gelato.unsw.edu.au> User-Agent: Mozilla-Thunderbird 2.0.0.4 (X11/20070622) MIME-Version: 1.0 CC: "Alan D. Brunelle" , Mathieu Desnoyers , linux-kernel@vger.kernel.org, btrace , Jens Axboe , Andrew Morton Subject: Re: Linux Kernel Markers - performance characterization with large IO load on large-ish system References: <46F92219.9020406@hp.com> <20070925171349.GA6057@Krystal> <46FA7A86.6090804@hp.com> <20071007193256.GA18558@elte.hu> In-Reply-To: <20071007193256.GA18558@elte.hu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1135 Lines: 27 Ingo Molnar wrote: > actually, the pure marker overhead seems to be a regression: > > Kernel Options Min val Avg val Max val Std Dev >> - markers - bt cfg 15.349127 16.169459 16.372980 0.184417 >> + markers - bt cfg 15.280382 16.202398 16.409257 0.191861 > > why isnt the marker near zero-cost as it should be? (as long as they are > enabled but are not in actual use) 2% increase is _ALOT_. The increase in the mean is actually 0.033, or 0.2%. > So there's something wrong going on - either markers have unacceptably > high cost, or the measurement is not valid. The third option is that the measurement just needs to be done more times. The standard error in the mean for the + markers case is 0.191861 / sqrt(10) = 0.061, which is twice the size of the difference being measured. -- Joshua Root, jmr AT gelato.unsw.edu.au http://www.gelato.unsw.edu.au - 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/