Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759566AbYHNSJ4 (ORCPT ); Thu, 14 Aug 2008 14:09:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752577AbYHNSJr (ORCPT ); Thu, 14 Aug 2008 14:09:47 -0400 Received: from tomts25.bellnexxia.net ([209.226.175.188]:41475 "EHLO tomts25-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752321AbYHNSJq (ORCPT ); Thu, 14 Aug 2008 14:09:46 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AswEAGQNpEhMRKxB/2dsb2JhbACBYrUigVU Date: Thu, 14 Aug 2008 14:09:43 -0400 From: Mathieu Desnoyers To: "H. Peter Anvin" Cc: Jeremy Fitzhardinge , Andi Kleen , Linus Torvalds , Ingo Molnar , Steven Rostedt , Steven Rostedt , LKML , Thomas Gleixner , Peter Zijlstra , Andrew Morton , David Miller , Roland McGrath , Ulrich Drepper , Rusty Russell , Gregory Haskins , Arnaldo Carvalho de Melo , "Luis Claudio R. Goncalves" , Clark Williams , Christoph Lameter Subject: Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug Message-ID: <20080814180943.GD4697@Krystal> References: <20080813200119.GA18966@Krystal> <20080813234156.GA25775@Krystal> <48A375E3.9090609@zytor.com> <48A388CE.2020404@goop.org> <20080814014944.GA31883@Krystal> <48A3A806.8060509@goop.org> <20080814151805.GA29507@Krystal> <48A459B1.2070601@zytor.com> <20080814165802.GC517@Krystal> <48A46897.4040900@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <48A46897.4040900@zytor.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 13:57:20 up 70 days, 22:37, 7 users, load average: 0.18, 0.68, 0.71 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 37 * H. Peter Anvin (hpa@zytor.com) wrote: > Mathieu Desnoyers wrote: >> Sure, here are the updated tables. Basically, they show no significant >> difference between the NOP and the DS segment selector prefix >> approaches. > > Actually, unless I have blown my T-test completely, they show with a 80% > and 74% confidence (respective for the two benchmarks) that the DS case is > slightly *better* (0.26% and 0.20% better, respective), which makes it a > no-brainer. Doing around 10 runs of each is likely to confirm this > conclusion by pushing it into the 90+% interval. > Yes, I think you are right. > Note that since the difference is so small, and so can also be due to some > kind of systematic error (lower ambient temperature during the DS run > making the disk drive slightly faster, what have you.) > I doubt it, because I made a "cache priming" run before the tests, which made sure the data was all populated in memory. But yeah, having different cpu clock calibration values/cpu clock frequency between reboots could also cause that kind of difference. Mathieu > -hpa -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/