Re: the trouble with large pages

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

On Fri, 2007-09-07 at 09:40 -0500, Hollis Blanchard wrote:
> The PowerPC 440 Linux kernel uses 256MB pages for the linear mapping.
> When we run that as a guest, those pages would of course need to be
> physically contiguous in the host.
> 
> I think long-term the KVM plan is to move memory allocation out of the
> kernel (where it currently uses vmalloc) into userspace, with the idea
> being that userspace could allocate memory via hugetlbfs. Anybody tried
> hugetlbfs on 440 or e500?
> 
> A poor-man's equivalent might be to limit the host memory to e.g. 256MB,
> then have userspace mmap(/dev/ram) starting there.
> 
> Another possibility is to fake out guest large pages by actually using
> small pages on the host, and handle the extra faults in KVM without
> notifying the guest.

This is what is done on x86.

Regards,

Anthony Liguori



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