From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265728AbTL3KSD (ORCPT ); Tue, 30 Dec 2003 05:18:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265729AbTL3KSD (ORCPT ); Tue, 30 Dec 2003 05:18:03 -0500 Received: from adsl-206-170-148-147.dsl.snfc21.pacbell.net ([206.170.148.147]:28570 "EHLO gw.goop.org") by vger.kernel.org with ESMTP id S265728AbTL3KSB (ORCPT ); Tue, 30 Dec 2003 05:18:01 -0500 Subject: Re: [PATCH] optimize ia32 memmove From: Jeremy Fitzhardinge To: Linus Torvalds Cc: Jeff Garzik , Andrew Morton , manfred@colorfullife.com, Linux Kernel List In-Reply-To: References: <200312300713.hBU7DGC4024213@hera.kernel.org> <3FF129F9.7080703@pobox.com> <20031229235158.755e026c.akpm@osdl.org> <3FF12FC7.5030202@pobox.com> Content-Type: text/plain Message-Id: <1072779479.16344.95.camel@ixodes.goop.org> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 (1.4.5-7) Date: Tue, 30 Dec 2003 02:17:59 -0800 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2003-12-30 at 01:58, Linus Torvalds wrote: > But then anything that does the loads in ascending order is still ok, so > it shouldn't matter - by the time "dest" has been overwritten, the source > data has already been read. And all the "memcpy()" implementations had > better do that anyway, in order to get nice memory access patterns. "rep > movsl" certainly does. A PPC memcpy may end up clearing the destination before reading the source (using the cache-line zeroing instruction, to prevent the destination from being spuriously read to populate the cache line). J