From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 21 May 2001 06:20:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 21 May 2001 06:20:03 -0400 Received: from pizda.ninka.net ([216.101.162.242]:48000 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Mon, 21 May 2001 06:19:55 -0400 From: "David S. Miller" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15112.60362.447922.780857@pizda.ninka.net> Date: Mon, 21 May 2001 03:19:54 -0700 (PDT) To: Andrea Arcangeli , Andrew Morton , Ivan Kokshaysky , Richard Henderson , linux-kernel@vger.kernel.org Subject: Re: alpha iommu fixes In-Reply-To: <15112.59880.127047.315855@pizda.ninka.net> In-Reply-To: <20010520044013.A18119@athlon.random> <3B07AF49.5A85205F@uow.edu.au> <20010520154958.E18119@athlon.random> <3B07CF20.2ABB5468@uow.edu.au> <20010520163323.G18119@athlon.random> <15112.26868.5999.368209@pizda.ninka.net> <20010521034726.G30738@athlon.random> <15112.48708.639090.348990@pizda.ninka.net> <20010521105944.H30738@athlon.random> <15112.55709.565823.676709@pizda.ninka.net> <20010521115631.I30738@athlon.random> <15112.59880.127047.315855@pizda.ninka.net> X-Mailer: VM 6.75 under 21.1 (patch 13) "Crater Lake" XEmacs Lucid Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David S. Miller writes: > > 1) I showed you in a private email that I calculated the > maximum possible IOMMU space that one could allocate > to bttv cards in a fully loaded Sunfire sparc64 system > to be between 300MB and 400MB. This is assuming that > every PCI slot contained a bttv card, and it still > used only ~%35 of the available IOMMU resources. This is totally wrong in two ways. Let me fix this, the IOMMU on these machines is per PCI bus, so this figure should be drastically lower. Electrically (someone correct me, I'm probably wrong) PCI is limited to 6 physical plug-in slots I believe, let's say it's 8 to choose an arbitrary larger number to be safe. Then we have: max bytes per bttv: max_gbuffers * max_gbufsize 64 * 0x208000 == 133.12MB 133.12MB * 8 PCI slots == ~1.06 GB Which is still only half of the total IOMMU space available per controller. Later, David S. Miller davem@redhat.com