mm: numa: do not clear PMD during PTE update scan
authorMel Gorman <mgorman@suse.de>
Thu, 19 Dec 2013 01:08:36 +0000 (17:08 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 19 Dec 2013 03:04:51 +0000 (19:04 -0800)
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>
mm/huge_memory.c

index 51f069303ab9e956f85187f42c141d629612f9b7..420826efda48f681c1f7518cb6bd5ebb76cb800d 100644 (file)
@@ -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;
                        }