From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754764AbYDHO3i (ORCPT ); Tue, 8 Apr 2008 10:29:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752888AbYDHO3b (ORCPT ); Tue, 8 Apr 2008 10:29:31 -0400 Received: from outbound-mail-20.bluehost.com ([69.89.20.235]:39714 "HELO outbound-mail-20.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752590AbYDHO3a convert rfc822-to-8bit (ORCPT ); Tue, 8 Apr 2008 10:29:30 -0400 From: Jesse Barnes To: Thomas =?iso-8859-1?q?Hellstr=F6m?= Subject: Re: [PATCH] x86: create array based interface to change page attribute Date: Tue, 8 Apr 2008 07:27:27 -0700 User-Agent: KMail/1.9.9 Cc: Arjan van de Ven , Andi Kleen , Dave Airlie , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com References: <1206940788.7250.13.camel@clockmaker.usersys.redhat.com> <200804071404.28691.jbarnes@virtuousgeek.org> <47FB0EE8.30001@tungstengraphics.com> In-Reply-To: <47FB0EE8.30001@tungstengraphics.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Message-Id: <200804080727.27309.jbarnes@virtuousgeek.org> X-Identified-User: {642:box128.bluehost.com:virtuous:virtuousgeek.org} {sentby:smtp auth 75.111.27.49 authed with jbarnes@virtuousgeek.org} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, April 07, 2008 11:21 pm Thomas Hellström wrote: > Jesse Barnes wrote: > > On Monday, April 07, 2008 1:46 pm Thomas Hellström wrote: > >>> Why would we need to flush at all at unbind-read-bind time? We should > >>> be able to leave pages in the WC state even when we unbind them, then > >>> when we need to bind them back into the GTT they'll be ready, but maybe > >>> I'm misunderstanding you here... > >> > >> We want to make the user-space mapping cache-coherent after unbind > >> during read, to have any serious read-speed, and the linear kernel map > >> has to follow, unless it's non-present. Even if it's non present, we > >> need to flush whatever was written through the user-space mapping from > >> the cache when rebinding. Having the user-space mapping read-only when > >> possible will help avoid this. > > > > Ah, you actually want to *read* from memory? Yeah that would be really > > slow if we left it UC or WC. But I thought that was really only > > necessary for relocation, and keithp dealt with that with the "presumed > > offset" stuff? Are you seeing other cases where we need to read back > > frequently? > > While keithp's "presumed offset" is really good stuff, we should never > need to read from device memory during relocations, I think. I was > thinking of EXA and OpenGL software fallback cases, "download from > screen" and "readpixels" types of operation, as well as > pixel-buffer-object map in read mode. Hm, yeah, anholt was telling me about some of these cases offline too. This is what makes things really difficult... Jesse