more than 3 GB in userspace (4G/4G patch?) for 2.6.16

more than 3 GB in userspace (4G/4G patch?) for 2.6.16

[Hanno Mueller]

Hi,

on my 8 GB system with two 32-bit-xeons, I would like to have more than
3 gigs in userspace.

A 0.5/3.5 GB split appears to be what I need for my application.

I read about the 4G/4G patch from 2004 but couldn't find a current patch
for 2.6.16 - is there anything similar to it that I can apply on a
2.6.16 kernel?

Thanks a lot & regards,

Hanno

Re: more than 3 GB in userspace (4G/4G patch?) for 2.6.16

[H. Peter Anvin]

Followup to:  <448F207A.6080601@hanno.de>
By author:    Hanno Mueller <sockpuppet@hanno.de>
In newsgroup: linux.dev.kernel
> 
> on my 8 GB system with two 32-bit-xeons, I would like to have more than
> 3 gigs in userspace.
> 

See if you can replace them with 64-bit Xeons.  That would be the best option.

> A 0.5/3.5 GB split appears to be what I need for my application.

That is incompatible with PAE.  The way PAE works, the split has to be
an even number of gigabytes.

	-hpa

Re: more than 3 GB in userspace (4G/4G patch?) for 2.6.16

[Dave Hansen]

On Tue, 2006-06-13 at 14:30 -0700, H. Peter Anvin wrote:
> > A 0.5/3.5 GB split appears to be what I need for my application.
> 
> That is incompatible with PAE.  The way PAE works, the split has to be
> an even number of gigabytes. 

Well, there have been ancient patches available in the past.  People pop
up now and again and ask for them.  This is _horribly_ out of date, but
it at least indicates that this is possible.

The basic idea is that you never share a kernel PMD page.  Each process
needs to allocate four of its own:

http://lkml.org/lkml/2003/5/9/138

-- Dave