Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760678AbYFDMDR (ORCPT ); Wed, 4 Jun 2008 08:03:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754392AbYFDMDF (ORCPT ); Wed, 4 Jun 2008 08:03:05 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:55954 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750764AbYFDMDC convert rfc822-to-8bit (ORCPT ); Wed, 4 Jun 2008 08:03:02 -0400 Date: Wed, 4 Jun 2008 12:47:14 +0100 From: Alan Cox To: Linus Torvalds Cc: Nick Piggin , Trent Piepho , Russell King , Benjamin Herrenschmidt , David Miller , linux-arch@vger.kernel.org, scottwood@freescale.com, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: MMIO and gcc re-ordering issue Message-ID: <20080604124714.55dbce65@core> In-Reply-To: References: <1211852026.3286.36.camel@pasglop> <200806041205.45833.nickpiggin@yahoo.com.au> X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 842 Lines: 20 > Anyway, Intel certainly seems to document that WC memory is serialized by > any access to UC memory. I don't believe that is actually true on Pentium Pro at least. > So what started out as a "we can do accesses to the frame buffer more > efficiently without anybody ever even having to know or care" has > turned into a whole nightmare of people using it for other things, and > then you very much _do_ have to care! ] Notably graphics where 3Dfx lined the registers up specifically to make this work. We were also using it with I²O where it gave a small performance gain. Alan -- 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/