linux-kernel - Re: Why is "Memory split" Kconfig option only for EMBEDDED?

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Message-Id: <1165679105.7455.116.camel@titan.tbdnetworks.com>
Date:	Sat, 09 Dec 2006 16:45:04 +0100
From:	Norbert Kiesel <nkiesel@...networks.com>
To:	Alejandro Riveira Fernández 
	<ariveira@...il.com>
Cc:	Adrian Bunk <bunk@...sta.de>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: Why is "Memory split" Kconfig option only for EMBEDDED?

On Sat, 2006-12-09 at 13:27 +0100, Alejandro Riveira Fernández wrote:
> El Wed, 6 Dec 2006 14:10:03 +0100
> Adrian Bunk <bunk@...sta.de> escribió:
> 
> > On Wed, Dec 06, 2006 at 01:19:08PM +0100, Norbert Kiesel wrote:
> > > On Wed, 2006-12-06 at 12:58 +0100, Arjan van de Ven wrote:
> > > > On Wed, 2006-12-06 at 12:42 +0100, Norbert Kiesel wrote:
> > > > > Hi,
> > > > > 
> > > > > I remember reading on LKML some time ago that using VMSPLIT_3G_OPT would
> > > > > be optimal for a machine with exactly 1GB memory (like my current
> > > > > desktop). Why is that option only prompted for after selecting EMBEDDED
> > > > > (which I normally don't select for desktop machines
> > > > 
> > > > because it changes the userspace ABI and has some other caveats.... this
> > > > is not something you should muck with lightly 
> > > > 
> > > 
> > > Hmm, but it's also marked EXPERIMENTAL. Would that not be the
> > > sufficient?  Assuming I don't use any external/binary drivers and a
> > > self-compiled kernel w//o any additional patches: is there really any
> > > downside?
> > 
> > - Wine doesn't work (I'm not sure about VMSPLIT_3G_OPT, but
> >                      VMSPLIT_2G definitely breaks Wine)
> 
>  I use VMSPLIT_3G_OPT=y and wine works just fine (only tested with one
>  program). Edgy + 2.6.19-rc1
> 
> 
> 
> > - AFAIR some people reported problems with some Java programs
> >   after fiddling with the vmsplit options
> > 
> > EMBEDDED isn't exactly the right way to hide it, but the vmsplit options 
> > aren't something you can safely change.
> > 

So far all first-hand experiences I heard of were positive (i.e. I did
not get an emaail from anyone saying: It had a negative effect for me),
so I propose to apply the patch from Con Kolivas. The wording in the
description still very strongly recommends to not change that value, and
it's still dependent on EXPERIMENTAL. I append the patch just because
it's short, it's also available from
http://www.kernel.org/pub/linux/kernel/people/ck/patches/2.6/2.6.19/2.6.19-ck2/patches/kconfig-expose_vmsplit_option.patch

The options to alter the vmsplit to enable more lowmem are hidden behind the
embedded option. Make it more exposed for -ck users and make the help menu
more explicit about what each option means.

Signed-off-by: Con Kolivas <kernel@...ivas.org>

---
 arch/i386/Kconfig |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Index: linux-2.6.19-ck2/arch/i386/Kconfig
===================================================================
--- linux-2.6.19-ck2.orig/arch/i386/Kconfig	2006-11-30 11:30:32.000000000 +1100
+++ linux-2.6.19-ck2/arch/i386/Kconfig	2006-12-09 09:01:36.000000000 +1100
@@ -500,7 +500,7 @@ endchoice
 
 choice
 	depends on EXPERIMENTAL
-	prompt "Memory split" if EMBEDDED
+	prompt "Memory split"
 	default VMSPLIT_3G
 	help
 	  Select the desired split between kernel and user memory.
@@ -519,14 +519,14 @@ choice
 	  option alone!
 
 	config VMSPLIT_3G
-		bool "3G/1G user/kernel split"
+		bool "Default 896MB lowmem (3G/1G user/kernel split)"
 	config VMSPLIT_3G_OPT
 		depends on !HIGHMEM
-		bool "3G/1G user/kernel split (for full 1G low memory)"
+		bool "1GB lowmem (3G/1G user/kernel split)"
 	config VMSPLIT_2G
-		bool "2G/2G user/kernel split"
+		bool "2GB lowmem (2G/2G user/kernel split)"
 	config VMSPLIT_1G
-		bool "1G/3G user/kernel split"
+		bool "3GB lowmem (1G/3G user/kernel split)"
 endchoice
 
 config PAGE_OFFSET


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