Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758909AbXHRWtF (ORCPT ); Sat, 18 Aug 2007 18:49:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754257AbXHRWsl (ORCPT ); Sat, 18 Aug 2007 18:48:41 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:32883 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753709AbXHRWsj (ORCPT ); Sat, 18 Aug 2007 18:48:39 -0400 Date: Sat, 18 Aug 2007 15:41:13 -0700 (PDT) From: Linus Torvalds To: "Paul E. McKenney" 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 In-Reply-To: <20070818215409.GC7628@linux.vnet.ibm.com> Message-ID: References: <46C505B2.6030704@yahoo.com.au> <18117.4848.695269.72976@cargo.ozlabs.ibm.com> <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 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1066 Lines: 25 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.. Linus - 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/