Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755600AbXKWJqj (ORCPT ); Fri, 23 Nov 2007 04:46:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753442AbXKWJqa (ORCPT ); Fri, 23 Nov 2007 04:46:30 -0500 Received: from poesci.dolphinics.no ([81.175.23.36]:48805 "EHLO poesci.dolphinics.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753425AbXKWJq3 (ORCPT ); Fri, 23 Nov 2007 04:46:29 -0500 To: dean gaudet Cc: Alan Cox , Daniel Drake , linux-kernel@vger.kernel.org, davem@davemloft.net, kune@deine-taler.de, johannes@sipsolutions.net Subject: Re: [RFC] Documentation about unaligned memory access References: <20071123001554.12F8B9D4A1F@zog.reactivated.net> <20071123012911.3266dba6@the-village.bc.nu> From: Arne Georg Gleditsch Date: Fri, 23 Nov 2007 10:46:31 +0100 In-Reply-To: (dean gaudet's message of "Thu\, 22 Nov 2007 22\:18\:28 -0800 \(PST\)") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/23.0.60 (gnu/linux) 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: 669 Lines: 16 dean gaudet writes: > on AMD x86 pre-family 10h the boundary is 8 bytes, and on fam 10h it's 16 > bytes. the penalty is a mere 3 cycles if an access crosses the specified > boundary. Worth noting though, is that atomic accesses that cross cache lines on an Opteron system is going to lock down the Hypertransport fabric for you during the operation -- which is obviously not so nice. -- Arne. - 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/