RFC: Hugepage COW

David Gibson david at gibson.dropbear.id.au
Thu Jul 7 19:24:25 EST 2005

On Thu, Jul 07, 2005 at 09:49:27AM +0300, Avi Kivity wrote:
> On Thu, 2005-07-07 at 15:55 +1000, David Gibson wrote:
> > MAP_PRIVATE|MAP_WRITE mappings of hugetlbfs.  Because the pool of
> > hugepages is limited, a write to a MAP_PRIVATE hugepage region may
> > result in a SIGBUS, if a new hugepage cannot be allocated.  This patch
> in that case you might allocate regular pages for the new copy.

That's not necessarily possible.  On some archs - ppc64 for one -
the mmu has to be set up for hugepages on a granularity greater than
the hugepage size.  So you can just arbitrarily substitute normal
pages for hugepages.

David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!

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