From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756824AbYBRSQk (ORCPT ); Mon, 18 Feb 2008 13:16:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752419AbYBRSQb (ORCPT ); Mon, 18 Feb 2008 13:16:31 -0500 Received: from one.firstfloor.org ([213.235.205.2]:52411 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752613AbYBRSQ3 (ORCPT ); Mon, 18 Feb 2008 13:16:29 -0500 Date: Mon, 18 Feb 2008 19:52:28 +0100 From: Andi Kleen To: Arjan van de Ven Cc: Andi Kleen , Frans Pop , linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: Unable to continue testing of 2.6.25 Message-ID: <20080218185228.GA29026@one.firstfloor.org> References: <200802171025.30590.elendil@planet.nl> <20080217124650.576990ce@laptopd505.fenrus.org> <20080218085018.05f3190a@laptopd505.fenrus.org> <20080218171159.GA24090@basil.nowhere.org> <20080218093215.5cf611a8@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080218093215.5cf611a8@laptopd505.fenrus.org> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I've yet to see a user who wants WC. Lets face it, WC *sucks*. This is why Interesting. > the folks who care about performance (the graphics guys) stopped using it. I didn't know this. What do they do instead? I understand that WC was added originally because AGP was really slow at IO towards the CPU. You mean on PCI-E it is fast enough now that standard cached WB works well enough? > WC is slow, and on modern cpus leads to really bad performance. I'm really > half tempted to just ignore WC entirely and suggest that we don't even implement > it in the kernel. Yes it's really that bad. At least the X server still uses it. In fact there are already some performance regression regarding this from differing kernel behavioun in the sysfs interfaces vs /dev/mem. What would you recommend should the X server use instead? Always map standard WB? How about on older AGP systems? -Andi