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

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Date:	Mon,  8 Jun 2015 14:56:31 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Linux-MM <linux-mm@...ck.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 25/25] mm: page_alloc: Take fewer passes when allocating to the low watermark

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 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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