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Date: Thu, 02 Oct 2014 12:19:11 -0400 From: Rik van Riel <riel@...hat.com> To: Mel Gorman <mgorman@...e.de>, Dave Jones <davej@...hat.com> CC: Linus Torvalds <torvalds@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>, Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>, Michel Lespinasse <walken@...gle.com>, Kirill A Shutemov <kirill.shutemov@...ux.intel.com>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 4/4] mm: numa: Do not mark PTEs pte_numa when splitting huge pages On 10/02/2014 09:29 AM, 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@...e.de> Acked-by: Rik van Riel <riel@...hat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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