[PATCH] hugetlb: powerpc: Actively close unused htlb regions on vma close

[Hugh Dickins]

On Fri, 2 Jun 2006, Adam Litke wrote:
> 
> On powerpc, each segment can contain pages of only one size.  When a
> hugetlb mapping is requested, a segment is located and marked for use
> with huge pages.  This is a uni-directional operation -- hugetlb
> segments are never marked for use again with normal pages.  For long
> running processes which make use of a combination of normal and hugetlb
> mappings, this behavior can unduly constrain the virtual address space.
> 
> The following patch introduces a architecture-specific vm_ops.close()
> hook.  For all architectures besides powerpc, this is a no-op.  On
> powerpc, the low and high segments are scanned to locate empty hugetlb
> segments which can be made available for normal mappings.  Comments?

Wouldn't hugetlb_free_pgd_range be a better place to do that kind of
thing, all within arch/powerpc, no need for arch_hugetlb_close_vma etc?

Hugh