[RFC 02/13] mm, page_alloc: set alloc_flags only once in slowpath

Vlastimil Babka
2016-05-10T07:37:12Z

In __alloc_pages_slowpath(), alloc_flags doesn't change after it's initialized,
so move the initialization above the retry: label. Also make the comment above
the initialization more descriptive.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/page_alloc.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a50184ec6ca0..91fbf6f95403 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3579,17 +3579,17 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
gfp_mask &= ~__GFP_ATOMIC;

-retry:
- if (gfp_mask & __GFP_KSWAPD_RECLAIM)
- wake_all_kswapds(order, ac);
-
/*
- * OK, we're below the kswapd watermark and have kicked background
- * reclaim. Now things get more complex, so set up alloc_flags according
- * to how we want to proceed.
+ * The fast path uses conservative alloc_flags to succeed only until
+ * kswapd needs to be woken up, and to avoid the cost of setting up
+ * alloc_flags precisely. So we do that now.
*/
alloc_flags = gfp_to_alloc_flags(gfp_mask);

+retry:
+ if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+ wake_all_kswapds(order, ac);
+
/* This is the last chance, in general, before the goto nopage. */
page = get_page_from_freelist(gfp_mask, order,
alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
--
2.8.2