From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261320AbVFAHsW (ORCPT ); Wed, 1 Jun 2005 03:48:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261321AbVFAHsW (ORCPT ); Wed, 1 Jun 2005 03:48:22 -0400 Received: from one.firstfloor.org ([213.235.205.2]:10133 "EHLO one.firstfloor.org") by vger.kernel.org with ESMTP id S261320AbVFAHsT (ORCPT ); Wed, 1 Jun 2005 03:48:19 -0400 To: michael@optusnet.com.au Cc: Denis Vlasenko , dean gaudet , Jeff Garzik , Benjamin LaHaise , linux-kernel@vger.kernel.org Subject: Re: [RFC] x86-64: Use SSE for copy_page and clear_page References: <20050530181626.GA10212@kvack.org> <20050530193225.GC25794@muc.de> <200505311137.00011.vda@ilport.com.ua> <200505311215.06495.vda@ilport.com.ua> <20050531092358.GA9372@muc.de> From: Andi Kleen Date: Wed, 01 Jun 2005 09:48:17 +0200 In-Reply-To: (michael@optusnet.com.au's message of "01 Jun 2005 17:22:28 +1000") Message-ID: User-Agent: Gnus/5.110002 (No Gnus v0.2) Emacs/21.3 (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 michael@optusnet.com.au writes: > > Key point: "using it". This normally involves writes to memory. Most > applications don't commonly read memory that they haven't previously > written to. (valgrind et al call that behaviour a "bug" :). > > Given that, I'd say you really don't want the page zero routines > touching the cache. Writing on a modern CPU requires reading first too to get the rest of the cache line (provided you don't use write combing or uncached accesses) -Andi