From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761363AbYDBVgS (ORCPT ); Wed, 2 Apr 2008 17:36:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756814AbYDBVgH (ORCPT ); Wed, 2 Apr 2008 17:36:07 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:37266 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755078AbYDBVgG (ORCPT ); Wed, 2 Apr 2008 17:36:06 -0400 Date: Wed, 2 Apr 2008 14:35:25 -0700 (PDT) From: Linus Torvalds To: Mikulas Patocka cc: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH]: Fix SMP-reordering race in mark_buffer_dirty In-Reply-To: Message-ID: References: User-Agent: Alpine 1.00 (LFD 882 2007-12-20) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2 Apr 2008, Linus Torvalds wrote: > > Core 2 is the outlier in having a noticeably faster "mfence" than atomic > instructions Side note: mfence is probably faster than 6 cycles on Core 2. I've seen it be basically zero-cost. Try adding a few memory ops around it - the timing will probably change. Core 2 has this odd behaviour that it sometimes does worse on the *really* trivial things that don't happen in real life. Linus