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

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Message-ID: <Pine.LNX.4.61.0612062158010.16042@yvahk01.tjqt.qr>
Date:	Wed, 6 Dec 2006 22:00:55 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Norbert Kiesel <nkiesel@...networks.com>
cc:	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: Why is "Memory split" Kconfig option only for EMBEDDED?


On Dec 6 2006 14:36, Norbert Kiesel wrote:
>On Wed, 2006-12-06 at 13:45 +0100, Arjan van de Ven wrote:
>> On Wed, 2006-12-06 at 13:19 +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?
>> 
>> I said *userspace ABI*. You're changing something that
>> userspace has known about and was documented since the start
>> of Linux. So userspace application binaries can break, and at
>> least you're changing the rules on them. That's fine if you
>> know what you're doing.. but in a general system... not a
>> good default, hence the EMBEDDED.
>
>Thanks for the reply. I was not asking to change the default, I
>just want to see the option in e.g. menuconfig. And the help
>text already has a very strong advise to leave it at
>VMSPLIT_3G.

I have not had yet any problems with VMSPLIT_3G_OPT ever since I
used it -- which dates back to when it was a feature of Con
Kolivas's patchset (known as LOWMEM1G), [even] before it got
merged in mainline.

It only seem to break the VMware compilation process, but what
they do in the makefiles is not really standard anyhow.

>Anyway, I don't want to stress this further: I'm happy enough with my
>Kconfig that has "if EMBEDDED" removed for the prompt. 



	-`J'
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