From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+willy=40w.ods.org-S932453AbWAJSOc@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932453AbWAJSOc (ORCPT <rfc822;willy@w.ods.org>);
	Tue, 10 Jan 2006 13:14:32 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932464AbWAJSOc
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Tue, 10 Jan 2006 13:14:32 -0500
Received: from dvhart.com ([64.146.134.43]:897 "EHLO dvhart.com")
	by vger.kernel.org with ESMTP id S932453AbWAJSOc (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 10 Jan 2006 13:14:32 -0500
Message-ID: <43C3F986.4090209@mbligh.org>
Date: Tue, 10 Jan 2006 10:14:30 -0800
From: Martin Bligh <mbligh@mbligh.org>
User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051011)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: Linus Torvalds <torvalds@osdl.org>
Cc: Jens Axboe <axboe@suse.de>, Byron Stanoszek <gandalf@winds.org>,
       Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>
Subject: Re: 2G memory split
References: <20060110125852.GA3389@suse.de> <20060110132957.GA28666@elte.hu> <20060110133728.GB3389@suse.de> <Pine.LNX.4.63.0601100840400.9511@winds.org> <20060110143931.GM3389@suse.de> <Pine.LNX.4.64.0601100804380.4939@g5.osdl.org>
In-Reply-To: <Pine.LNX.4.64.0601100804380.4939@g5.osdl.org>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

Linus Torvalds wrote:
> 
> On Tue, 10 Jan 2006, Jens Axboe wrote:
> 
>>A newer version, trying to cater to the various comments in here.
>>Changes:
> 
> 
> Can we do one final cleanup? Do all the magic in _one_ place, namely the 
> x86 Kconfig file.
> 
> Also, I don't think the NOHIGHMEM dependency is necessarily correct. A 
> 2G/2G split can be advantageous with a 16GB setup (you'll have more room 
> for dentries etc), but you obviously want to have HIGHMEM for that..
> 
> Do it something like this:
> 
> 	choice
> 		depends on EXPERIMENTAL
> 		prompt "Memory split"
> 		default DEFAULT_3G
> 		help
> 		  Select the wanted split between kernel and user memory.
> 		  If the address range available to the kernel is less than the
> 		  physical memory installed, the remaining memory will be available
> 		  as "high memory". Accessing high memory is a little more costly
> 		  than low memory, as it needs to be mapped into the kernel first.
> 		  Note that selecting anything but the default 3G/1G split will make
> 		  your kernel incompatible with binary only modules.
> 
> 		config DEFAULT_3G
> 			bool "3G/1G user/kernel split"
> 		config DEFAULT_3G_OPT
> 			bool "3G/1G user/kernel split (for full 1G low memory)"
> 		config DEFAULT_2G
> 			bool "2G/2G user/kernel split"
> 		config DEFAULT_1G
> 			bool "1G/3G user/kernel split"
> 	endchoice
> 
> 	config PAGE_OFFSET
> 		hex
> 		default 0xC0000000
> 		default 0xB0000000 if DEFAULT_3G_OPT
> 		default 0x78000000 if DEFAULT_2G
> 		default 0x40000000 if DEFAULT_1G
> 
> and then asm-i386/page.h can just do
> 
> 	#define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)
> 
> and you're done.

The non-1GB-aligned ones need to be disbarred when PAE is on, I think.

M.