From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267406AbUHDUQo (ORCPT ); Wed, 4 Aug 2004 16:16:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267407AbUHDUQo (ORCPT ); Wed, 4 Aug 2004 16:16:44 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.104]:26504 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S267406AbUHDUQl (ORCPT ); Wed, 4 Aug 2004 16:16:41 -0400 Date: Wed, 04 Aug 2004 13:13:56 -0700 From: "Martin J. Bligh" To: Roland Dreier cc: Andrew Morton , Jens Axboe , eric@cisu.net, kernel@kolivas.org, barryn@pobox.com, swsnyder@insightbb.com, linux-kernel@vger.kernel.org Subject: Re: HIGHMEM4G config for 1GB RAM on desktop? Message-ID: <214180000.1091650436@flay> In-Reply-To: <527jseis2g.fsf@topspin.com> References: <200408021602.34320.swsnyder@insightbb.com><410FA145.70701@kolivas.org> <20040804060625.GE10340@suse.de><200408040614.30820.eric@cisu.net> <20040804130707.GN10340@suse.de><20040804120633.4dca57b3.akpm@osdl.org> <210450000.1091647829@flay> <527jseis2g.fsf@topspin.com> X-Mailer: Mulberry/2.1.2 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Martin> I had a patch for a config option, ported forward by > Martin> someone at IBM (I forget who, possibly Dave) from Andrea's > Martin> original. I think we finally decided (in consultation with > Martin> Andrea) we could drop the complicated stuff he had in the > Martin> asm code, so it's pretty simple ... something like this: > > Am I just being dense, or is this patch solving a different problem > from "do I really have to turn on HIGHMEM4G just to get the last 128MB > of my 1GB of RAM?" > > It seems to me that none of the PAGE_OFFSET values offered (the patch > in allows PAGE_OFFSET to be set to 0xe0000000, 0xc0000000, 0x80000000 > or 0x40000000, in addition to the 4G/4G value of 0x02000000) are > exactly what someone with 1 GB of RAM wants. They'd be forced to go > down to a 2G/2G split which cheats userspace of quite a bit of address > space (admittedly with only 1 GB of RAM, a process bigger than 2 GB is > a bit of a stretch). In any case a 2.75G/1.25G split as suggested > earlier works fine with 1 GB of RAM. In practice, I suspect 2/2 will do exactly what you want ... and what 99.9% of people want actually ;-) We could add more options, but be sure to mark anything that's not 1GB aligned as not suitable for PAE (as the 0.5 split was). > Also I notice that Con's patch modifies vmlinux.ld.S to update the > kernel base address, while this patch doesn't. Is that intentional or > is does the patch depend on some other patches that use the defines in > page.h somehow as controlled by the following change? > > +AFLAGS_vmlinux.lds.o += -include $(TOPDIR)/include/asm-i386/page.h Dunno ... we should test it really ... it's been a while. IIRC, vmlinux.ld.S was hardcoded, so I don't see how it'd work without those mods. M.