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[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>
This commit is contained in:
Nishanth Aravamudan 2006-08-31 21:27:53 -07:00 committed by Linus Torvalds
parent 1678df37be
commit 3b98b087fc
1 changed files with 9 additions and 1 deletions
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10
mm/mempolicy.c
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@ -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