Commit 5a6dac3e authored Dec 18, 2013 by Mel Gorman Committed by Linus Torvalds Dec 18, 2013

mm: numa: do not clear PMD during PTE update scan



If the PMD is flushed then a parallel fault in handle_mm_fault() will
enter the pmd_none and do_huge_pmd_anonymous_page() path where it'll
attempt to insert a huge zero page.  This is wasteful so the patch
avoids clearing the PMD when setting pmd_numa.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 67f87463

mm/huge_memory.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1539,7 +1539,7 @@ int change_huge_pmd(struct vm_area_struct vma, pmd_t pmd,
		*/
		if (!is_huge_zero_page(page) &&
		!pmd_numa(*pmd)) {
		entry = pmdp_get_and_clear(mm, addr, pmd);
		entry = *pmd;
		entry = pmd_mknuma(entry);
		ret = HPAGE_PMD_NR;
		}