From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 2 May 2002 14:27:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 2 May 2002 14:27:01 -0400 Received: from dsl-213-023-038-046.arcor-ip.net ([213.23.38.46]:18336 "EHLO starship") by vger.kernel.org with ESMTP id ; Thu, 2 May 2002 14:26:59 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Andrea Arcangeli , "Martin J. Bligh" Subject: Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?] Date: Thu, 2 May 2002 20:25:35 +0200 X-Mailer: KMail [version 1.3.2] Cc: Russell King , linux-kernel@vger.kernel.org In-Reply-To: <20020502180632.I11414@dualathlon.random> <3972036796.1020330599@[10.10.2.3]> <20020502184037.J11414@dualathlon.random> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 02 May 2002 18:40, Andrea Arcangeli wrote: > On Thu, May 02, 2002 at 09:10:00AM -0700, Martin J. Bligh wrote: > > > You can trivially map the phys mem between 1G and 1G+256M to be in a > > > direct mapping between 3G+256M and 3G+512M, then you can put such 256M > > > at offset 1G into the ZONE_NORMAL of node-id 1 with discontigmem too. > > > > > > The constraints you have on the normal memory are only two: > > > > > > 1) direct mapping > > > 2) DMA > > > > > > so as far as the ram is capable of 32bit DMA with pci32 and it's mapped > > > in the direct mapping you can put it into the normal zone. There is no > > > difference at all between discontimem or nonlinear in this sense. > > > > Now imagine an 8 node system, with 4Gb of memory in each node. > > First 4Gb is in node 0, second 4Gb is in node 1, etc. > > > > Even with 64 bit DMA, the real problem is breaking the assumption > > that mem between 0 and 896Mb phys maps 1-1 onto kernel space. > > That's 90% of the difficulty of what Dan's doing anyway, as I > > see it. > > You don't need any additional common code abstraction to make virtual > address 3G+256G to point to physical address 1G as in my example above, M ----^ > after that you're free to put the physical ram between 1G and 1G+256M > into the zone normal of node 1 and the stuff should keep working but > with zone-normal spread in more than one node. I don't see that you accomplished that at all, with config_discontig. How can you address the memory at 3G+256M? That looks like highmem to me. No good at all for kmem caches, buffers, struct pages, etc. Without config_nonlinear, those structures will all have to be off-node for most nodes. -- Daniel