Commit 3b98b087 authored Aug 31, 2006 by Nishanth Aravamudan Committed by Linus Torvalds Sep 01, 2006

[PATCH] fix NUMA interleaving for huge pages



Since vma->vm_pgoff is in units of smallpages, VMAs for huge pages have the
lower HPAGE_SHIFT - PAGE_SHIFT bits always cleared, which results in badd
offsets to the interleave functions.  Take this difference from small pages
into account when calculating the offset.  This does add a 0-bit shift into
the small-page path (via alloc_page_vma()), but I think that is negligible.
 Also add a BUG_ON to prevent the offset from growing due to a negative
right-shift, which probably shouldn't be allowed anyways.

Tested on an 8-memory node ppc64 NUMA box and got the interleaving I
expected.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Acked-by: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 1678df37

mm/mempolicy.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -1176,7 +1176,15 @@ static inline unsigned interleave_nid(struct mempolicy *pol,
		if (vma) {
		unsigned long off;

		off = vma->vm_pgoff;
		/*
		* for small pages, there is no difference between
		* shift and PAGE_SHIFT, so the bit-shift is safe.
		* for huge pages, since vm_pgoff is in units of small
		* pages, we need to shift off the always 0 bits to get
		* a useful offset.
		*/
		BUG_ON(shift < PAGE_SHIFT);
		off = vma->vm_pgoff >> (shift - PAGE_SHIFT);
		off += (addr - vma->vm_start) >> shift;
		return offset_il_node(pol, vma, off);
		} else

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