Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759338AbXHRXTo (ORCPT ); Sat, 18 Aug 2007 19:19:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756548AbXHRXTc (ORCPT ); Sat, 18 Aug 2007 19:19:32 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:37055 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755812AbXHRXTa (ORCPT ); Sat, 18 Aug 2007 19:19:30 -0400 Date: Sat, 18 Aug 2007 16:19:24 -0700 From: "Paul E. McKenney" To: Linus Torvalds Cc: Satyam Sharma , Christoph Lameter , Herbert Xu , Nick Piggin , Paul Mackerras , Segher Boessenkool , heiko.carstens@de.ibm.com, horms@verge.net.au, linux-kernel@vger.kernel.org, rpjday@mindspring.com, ak@suse.de, netdev@vger.kernel.org, cfriesen@nortel.com, akpm@linux-foundation.org, jesper.juhl@gmail.com, linux-arch@vger.kernel.org, zlynx@acm.org, schwidefsky@de.ibm.com, Chris Snook , davem@davemloft.net, wensong@linux-vs.org, wjiang@resilience.com Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Message-ID: <20070818231924.GH7628@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <46C516BA.60700@yahoo.com.au> <20070817235912.GA24314@linux.vnet.ibm.com> <20070818000913.GA25585@gondor.apana.org.au> <20070818010818.GQ8464@linux.vnet.ibm.com> <20070818215409.GC7628@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1230 Lines: 30 On Sat, Aug 18, 2007 at 03:41:13PM -0700, Linus Torvalds wrote: > > > On Sat, 18 Aug 2007, Paul E. McKenney wrote: > > > > One of the gcc guys claimed that he thought that the two-instruction > > sequence would be faster on some x86 machines. I pointed out that > > there might be a concern about code size. I chose not to point out > > that people might also care about the other x86 machines. ;-) > > Some (very few) x86 uarchs do tend to prefer "load-store" like code > generation, and doing a "mov [mem],reg + op reg" instead of "op [mem]" can > actually be faster on some of them. Not any that are relevant today, > though. ;-) > Also, that has nothing to do with volatile, and should be controlled by > optimization flags (like -mtune). In fact, I thought there was a separate > flag to do that (ie something like "-mload-store"), but I can't find it, > so maybe that's just my fevered brain.. Good point, will suggest this if the need arises. Thanx, Paul - 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/