Messages in this thread | | | Date | Thu, 2 Oct 2014 18:18:07 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 4/4] mm: numa: Do not mark PTEs pte_numa when splitting huge pages |
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On Thu, Oct 02, 2014 at 02:29:18PM +0100, Mel Gorman wrote: > This patch reverts 1ba6e0b50b ("mm: numa: split_huge_page: transfer the > NUMA type from the pmd to the pte"). If a huge page is being split due > a protection change and the tail will be in a PROT_NONE vma then NUMA > hinting PTEs are temporarily created in the protected VMA. > > VM_RW|VM_PROTNONE > |-----------------| > ^ > split here > > In the specific case above, it should get fixed up by change_pte_range() > but there is a window of opportunity for weirdness to happen. Similarly, > if a huge page is shrunk and split during a protection update but before > pmd_numa is cleared then a pte_numa can be left behind. > > Instead of adding complexity trying to deal with the case, this patch > will not mark PTEs NUMA when splitting a huge page. NUMA hinting faults > will not be triggered which is marginal in comparison to the complexity > in dealing with the corner cases during THP split. > > Signed-off-by: Mel Gorman <mgorman@suse.de>
I think it deserves a comment to avoid re-introducing NUMA type transferring.
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
-- Kirill A. Shutemov
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