Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758785AbXHUGHR (ORCPT ); Tue, 21 Aug 2007 02:07:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755179AbXHUGHA (ORCPT ); Tue, 21 Aug 2007 02:07:00 -0400 Received: from py-out-1112.google.com ([64.233.166.179]:38208 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753909AbXHUGHA (ORCPT ); Tue, 21 Aug 2007 02:07:00 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Ch3DsGL7A8Oa6oUHuzPa3f3U4mRIjEZ8WPijXxP1w6eeq4edIOn6MX/d0ymcNNcwEqx56WIjuyqazBRQivdZBisNOk4RAjyTLGRiWQdPxROkytDYP2N2z1FQLSeGKRsWrwypAmqPNeQePUD9pIYCy8B8hQfCBTPDcktMr/KE1lU= Message-ID: <21d7e9970708202306nda9be8dl2d305eb5a80bfcf8@mail.gmail.com> Date: Tue, 21 Aug 2007 16:06:58 +1000 From: "Dave Airlie" To: "Daniel J Blueman" Subject: Re: uncached page allocator Cc: "Linux Kernel" In-Reply-To: <6278d2220708200536r786ee72ere7522547c375a428@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <6278d2220708200536r786ee72ere7522547c375a428@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1389 Lines: 38 > > Write-combining access seems the correct thing here, followed by a > wmb(). Uncached writing would be horrendously slow. > > [snip] > > So after all that I'd like to have some sort of uncached page list I > > can allocate pages from > > This is exactly what Intel's PAT mechanism exists for - just mark the > desired access type (index) on the pages you've been allocated. > > It's documented in the Intel Architecture Software Design manuals, but > Linux's support is lacking in certain areas [discussions on LKML], > which a number of developers have been trying to move forward. > > Quite a few significant graphics/HPC etc vendors are forced to use it > without this complete support, so it would be good to get this > additional impetus involved... I'm hoping to pick up the PAT cause at some point soon this stuff is definitely required to get any use out of modern graphics hardware. It is slightly orthogonal to the issue I mentioned in that I still have the problem of allocating uncached memory without the flushing overheads associated with making pages cached/uncached constantly.. Dave. > > Daniel > -- > Daniel J Blueman > - 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/