[OSM-dev] mmap() (was: Re: Some statistics for file-format -development)

Dave Hansen dave at sr71.net
Fri Dec 5 20:34:08 GMT 2008

On Fri, 2008-12-05 at 01:41 +0100, Sascha Silbe wrote:
> On Thu, Dec 04, 2008 at 03:20:02PM -0800, Dave Hansen wrote:
> >> I don't think that's possible. Both 32bit and 64bit userspace and 
> >> emulation work with a 64bit kernel, but at least 64bit userspace on a 
> >> 32bit kernel isn't possible.
> > Believe it or not, people actually do this on powerpc.
> Interesting. Is it possible on AMD64 as well? How does the additional 
> address space get managed?
> As this is getting off topic, I'd suggest to move to private mails.

It is possible, but not ever implemented.  amd64 doesn't have the same
disadvantages when you go 32->64 bits as ppc.  

The additional address space is managed no differently than it is on a
normal 32-bit system with more physical memory than can be addressed in
the normal kernel linear mapping.  (That's 2GB on Windows and 1GB on
most Linux systems).

-- Dave

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