[PATCH 25/25] mm: page_alloc: Take fewer passes when allocating to the low watermark

From: Mel Gorman
Date: Mon Jun 08 2015 - 09:58:15 EST


Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
mm/page_alloc.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 886102cc9b09..58f6330ec3e2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1927,6 +1927,27 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
if (alloc_flags & ALLOC_NO_WATERMARKS)
goto try_this_zone;

+ /*
+ * If checking the low watermark, see if we meet the
+ * min watermark and if so, try the zone and wake
+ * kswapd instead of falling back to a remote zone
+ * or having to take a second pass
+ */
+ if (alloc_flags & ALLOC_WMARK_LOW) {
+ int min_flags = alloc_flags;
+
+ min_flags &= ~ALLOC_WMARK_LOW;
+ min_flags |= ALLOC_WMARK_MIN;
+
+ if (zone_watermark_ok(zone, order,
+ zone->watermark[min_flags & ALLOC_WMARK_MASK],
+ ac->classzone_idx,
+ min_flags)) {
+ wakeup_kswapd(zone, order, ac->classzone_idx);
+ goto try_this_zone;
+ }
+ }
+
if (node_reclaim_mode == 0 ||
!zone_allows_reclaim(ac->preferred_zone, zone))
goto this_zone_full;
--
2.3.5

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