Re: 2.6.32-rc3: low mem - only 378MB on x86_32 with 64GB. Why?

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 6 Oct 2009, David Woodhouse wrote:

> On Mon, 2009-10-05 at 17:30 -0700, Linus Torvalds wrote:
> > In fact, I wish more people did that, just so that we'd get better 
> > coverage of the 32-bit compat code. We occasionally find issues there,
> > although I think it's getting rarer.
> 
> We've been running PPC64 with 32-bit userspace for a long time, so most
> of the issues with the 32-bit compat code ought to be dealt with.
> 
> There may be a few arch-specific issues for x86_64/i386, but not many.

The Intel Xorg guys used to do everything in 32-bit kernels because they 
were also testing that they didn't break compatibility (which is a big 
deal with that whole crazy DRM-in-kernel/direct-rendering-in-user-space 
thing) and seemingly didn't realize that the compat layer was _supposed_ 
to mean that they could run a 64-bit kernel and still have a working 
32-bit land.

It's driver interfaces like that that tend to break. ioctl's etc. But I 
have heard less noise about it lately, so I do think it's mostly working.

		Linus