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Message-ID: <17347.47882.735057.154898@alkaid.it.uu.se>
Date: Tue, 10 Jan 2006 14:47:54 +0100
From: Mikael Pettersson <mikpe@csd.uu.se>
To: Jens Axboe <axboe@suse.de>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
       Linus Torvalds <torvalds@osdl.org>
Subject: Re: 2G memory split
In-Reply-To: <20060110125852.GA3389@suse.de>
References: <20060110125852.GA3389@suse.de>
Sender: linux-kernel-owner@vger.kernel.org
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Jens Axboe writes:
 > Hi,
 > 
 > It does annoy me that any 1G i386 machine will end up with 1/8th of the
 > memory as highmem. A patch like this one has been used in various places
 > since the early 2.4 days at least, is there a reason why it isn't merged
 > yet? Note I just hacked this one up, but similar patches abound I'm
 > sure. Bugs are mine.
 > 
 > Signed-off-by: Jens Axboe <axboe@suse.de>
 > 
 > diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
 > index d849c68..0b2457b 100644
 > --- a/arch/i386/Kconfig
 > +++ b/arch/i386/Kconfig
 > @@ -444,6 +464,24 @@ config HIGHMEM64G
 >  
 >  endchoice
 >  
 > +choice
 > +	depends on NOHIGHMEM
 > +	prompt "Memory split"
 > +	default DEFAULT_3G
 > +	help
 > +	  Select the wanted split between kernel and user memory. On a 1G
 > +	  machine, the 3G/1G default split will result in 128MiB of high
 > +	  memory. Selecting a 2G/2G split will make all of memory available
 > +	  as low memory. Note that this will make your kernel incompatible
 > +	  with binary only kernel modules.

2G/2G is not the only viable alternative. On my 1GB x86 box I'm
using "lowmem1g" patches for both 2.4 and 2.6, which results in
2.75G for user-space. I'm sure others have other preferences.
Any standard option for this should either have several hard-coded
alternatives, or should support arbitrary values (within reason).

(See http://www.csd.uu.se/~mikpe/linux/patches/*/patch-i386-lowmem1g-*
if you're interested.)

/Mikael
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