Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762159AbXE3Wbj (ORCPT ); Wed, 30 May 2007 18:31:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752888AbXE3WbN (ORCPT ); Wed, 30 May 2007 18:31:13 -0400 Received: from terminus.zytor.com ([192.83.249.54]:38870 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbXE3WbL (ORCPT ); Wed, 30 May 2007 18:31:11 -0400 Message-ID: <465DFB25.4070009@zytor.com> Date: Wed, 30 May 2007 15:31:01 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Andi Kleen CC: Dave Airlie , Linus Torvalds , Linux Kernel Mailing List Subject: Re: GFP_DMA32 and PAE x86 machines References: <21d7e9970705301410m16ded9esdf7a49371c60a155@mail.gmail.com> <465DECD7.8030104@zytor.com> <21d7e9970705301507o2a89e824xdc6a980e8dbedaaf@mail.gmail.com> <200705310024.25937.ak@suse.de> In-Reply-To: <200705310024.25937.ak@suse.de> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1272 Lines: 31 Andi Kleen wrote: > On Thursday 31 May 2007 00:07:45 Dave Airlie wrote: >> Depending on split all lowmem is below 1GB which isn't exactly >> optimal, I'd llike all 4GB for DMA. > > Well it would be for a quite specialized limited use case: > - Memory the kernel doesn't need to map (after all kmap is evil) > - You need more than 500MB or so. > - 32bit kernel and user cannot run 64bit kernel > - Machine has >3GB of RAM There aren't really a whole lot of 32-bit boxen with > 4 GB of RAM (for 4 GB or less -- 2-3 GB or less if the chipset supports remapping -- normal HIGHMEM is all in the required area), and the few that are tend to be running specialized applications (git.kernel.org is one of those machines.) Since it appears that legacy memory standards, SDRAM and DDR-1, aren't dropping in price like DDR-2 is, I suspect that will more or less remain that way. The other problem -- which is a problem in general -- is the proliferation of DMA masks, and that doesn't look like it's going to get any better. -hpa - 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/