Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761651AbXJDSlX (ORCPT ); Thu, 4 Oct 2007 14:41:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759441AbXJDSlP (ORCPT ); Thu, 4 Oct 2007 14:41:15 -0400 Received: from mx1.redhat.com ([66.187.233.31]:43698 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756414AbXJDSlO (ORCPT ); Thu, 4 Oct 2007 14:41:14 -0400 Date: Thu, 4 Oct 2007 14:41:07 -0400 From: Dave Jones To: Andi Kleen Cc: Nick Piggin , Linux Kernel Mailing List , Linus Torvalds Subject: Re: [rfc][patch 2/3] x86: fix IO write barriers Message-ID: <20071004184107.GC23300@redhat.com> Mail-Followup-To: Dave Jones , Andi Kleen , Nick Piggin , Linux Kernel Mailing List , Linus Torvalds References: <20071004052153.GA15131@wotan.suse.de> <200710041953.16656.ak@suse.de> <20071004181044.GA23300@redhat.com> <200710042021.59704.ak@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200710042021.59704.ak@suse.de> User-Agent: Mutt/1.5.14 (2007-02-12) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1816 Lines: 56 On Thu, Oct 04, 2007 at 08:21:59PM +0200, Andi Kleen wrote: > On Thursday 04 October 2007 20:10:44 Dave Jones wrote: > > On Thu, Oct 04, 2007 at 07:53:16PM +0200, Andi Kleen wrote: > > > > > > > The only vendor that ever implemented OOSTOREs was Centaur, and they > > > > only did in the Winchip generation of the CPUs. When they dropped it > > > > from the C3, I asked whether they intended to bring it back, and the > > > > answer was "extremely unlikely". > > > > > > > > > > Do you know if it made a big performance difference? > > > > On the winchip, it was a huge win. I can't remember exact numbers, > > but pretty much every benchmark I threw at it at the time showed > > significant improvement. > > Significant as in >10%? "Worth about 10-20% performance" according to the 2.4.18pre9-ac4 release notes: http://www.linuxtoday.com/news_story.php3?ltsn=2002-02-14-015-20-NW-KN > > > But yes we should probably just remove this special case to make > > > maintenance easier. > > It's CONFIG_SMP anyway, which none of the winchips were. > > It's not. You're right it isn't now, but Nicks patch seems to change it so that it is. ... #ifdef CONFIG_SMP #define smp_mb() mb() #define smp_rmb() rmb() -#define smp_wmb() wmb() +#ifdef CONFIG_X86_OOSTORE +# define smp_wmb() wmb() +#else +# define smp_wmb() barrier() +#endif > And we need memory barriers even without SMP > when talking to device drivers. Only the smp_*b()s get noped > on UP. Good point. Dave -- http://www.codemonkey.org.uk - 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/