Commit da838d4f authored May 19, 2016 by Mel Gorman Committed by Linus Torvalds May 19, 2016

mm, page_alloc: pull out side effects from free_pages_check



Check without side-effects should be easier to maintain.  It also
removes the duplicated cpupid and flags reset done in !DEBUG_VM variant
of both free_pcp_prepare() and then bulkfree_pcp_prepare().  Finally, it
enables the next patch.

It shouldn't result in new branches, thanks to inlining of the check.

!DEBUG_VM bloat-o-meter:

  add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-27 (-27)
  function                                     old     new   delta
  __free_pages_ok                              748     739      -9
  free_pcppages_bulk                          1403    1385     -18

DEBUG_VM:

  add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-28 (-28)
  function                                     old     new   delta
  free_pages_prepare                           806     778     -28

This is also slightly faster because cpupid information is not set on
tail pages so we can avoid resets there.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent bb552ac6

mm/page_alloc.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -833,11 +833,8 @@ static void free_pages_check_bad(struct page *page)

		static inline int free_pages_check(struct page *page)
		{
		if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE))) {
		page_cpupid_reset_last(page);
		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
		if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
		return 0;
		}

		/* Something has gone sideways, find it */
		free_pages_check_bad(page);
		@@ -1078,7 +1075,11 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
		for (i = 1; i < (1 << order); i++) {
		if (compound)
		bad += free_tail_pages_check(page, page + i);
		bad += free_pages_check(page + i);
		if (unlikely(free_pages_check(page + i))) {
		bad++;
		continue;
		}
		(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
		}
		}
		if (PageAnonHead(page))
		@@ -1087,6 +1088,8 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
		if (bad)
		return false;

		page_cpupid_reset_last(page);
		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
		reset_page_owner(page, order);

		if (!PageHighMem(page)) {