From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750820AbWCaQhq (ORCPT ); Fri, 31 Mar 2006 11:37:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751395AbWCaQhq (ORCPT ); Fri, 31 Mar 2006 11:37:46 -0500 Received: from cantor.suse.de ([195.135.220.2]:47594 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1751380AbWCaQhn (ORCPT ); Fri, 31 Mar 2006 11:37:43 -0500 From: Andi Kleen To: Hans Boehm Subject: Re: Synchronizing Bit operations V2 Date: Fri, 31 Mar 2006 18:37:33 +0200 User-Agent: KMail/1.9.1 Cc: Christoph Lameter , Zoltan Menyhart , "Grundler, Grant G" , "Chen, Kenneth W" , akpm@osdl.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200603311837.34477.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Friday 31 March 2006 18:22, Hans Boehm wrote: > My impression is that approach (1) tends not to stick, since it involves > a substantial performance hit on architectures on which the fence is > not implicitly included in atomic operations. Those include Itanium and > PowerPC. At least the PPC people are eating the overhead because back when they didn't they had a long string of subtle powerpc only bugs caused by that It's a stability/maintainability vs performance issue. I doubt the performance advantage would be worth the additional work. I guess with the engineering time you would need to spend getting all this right you could do much more fruitful optimizations. -Andi