Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755464AbYHTKtX (ORCPT ); Wed, 20 Aug 2008 06:49:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752446AbYHTKtP (ORCPT ); Wed, 20 Aug 2008 06:49:15 -0400 Received: from smtpq1.groni1.gr.home.nl ([213.51.130.200]:44729 "EHLO smtpq1.groni1.gr.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752384AbYHTKtO (ORCPT ); Wed, 20 Aug 2008 06:49:14 -0400 Message-ID: <48ABF6DC.8070305@keyaccess.nl> Date: Wed, 20 Aug 2008 12:50:04 +0200 From: Rene Herman User-Agent: Thunderbird 2.0.0.16 (X11/20080707) MIME-Version: 1.0 To: Ingo Molnar CC: Venki Pallipadi , Dave Airlie , "Li, Shaohua" , Yinghai Lu , Andreas Herrmann , Arjan van de Ven , "dri-users@lists.sourceforge.net" , Linux Kernel , "Siddha, Suresh B" , Thomas Gleixner , "H. Peter Anvin" , Dave Jones Subject: Re: AGP and PAT (induced?) problem (on AMD family 6) References: <48972EA8.8040001@keyaccess.nl> <20080815142218.GC12954@elte.hu> <48A59FAC.7050605@keyaccess.nl> <48AA9C3B.5030309@keyaccess.nl> <20080819102633.GE6722@elte.hu> <48AAD680.7020508@keyaccess.nl> <20080819190757.GA17470@linux-os.sc.intel.com> <20080820100440.GE28492@elte.hu> In-Reply-To: <20080820100440.GE28492@elte.hu> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.0 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1801 Lines: 42 On 20-08-08 12:04, Ingo Molnar wrote: > * Venki Pallipadi wrote: > >>> I'd really like a reply from the AGP or PAT side right about now. >> Hmm. Looks like there are more than 16000 entries in the PAT list! > > hm, btw., why is that? Because 64M of AGP memory divided by 4K pages is 16K. That is, the underlying problem seems to be AGP drivers using order 0 allocations. I'm looking. Do note also that this means that Venki's change would not constitite a correct/final fix. Sure, caching the last entry speeds up traversing a 16K entry list but the issue is that there shouldn't be a 16K entry list. Through AGP, or maybe even by coalescing entries in the PAT list if that's at all possible (I guess it's not really). Even if such a more fundamental fix isn't (easily) available, the PAT code already comments that the list, which is sorted by ->start value, is expected to be short, and should be turned into an rbtree if it isn't which might be slightly less of a bandaid. Dave Airlie (as the MAINTAINERS entry) can't be arsed to answer email it seems so I've added Dave Jones for a possible comment from the AGP side. If I'm reading this right upto now, still many AGP driver (among which my amd-k7-agp) are affected. In the short run and if I'm not just mistaken, the best fix might be to make PAT dependent on not having a dumb AGP driver (but as said, still looking). Note that my chipset is capable of a 2G AGP aperture. That's 512K pages if fully used, 256K for 1G, 128K for 512M, ... Rene. -- 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/