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[PATCH 10/27] mm, vmscan: By default have direct reclaim only shrink once per node

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Direct reclaim iterates over all zones in the zonelist and shrinking them
but this is in conflict with node-based reclaim. In the default case,
only shrink once per node.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/vmscan.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0417f20aead7..fe004cb11b71 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2549,14 +2549,6 @@ static inline bool compaction_ready(struct zone *zone, int order)
  * try to reclaim pages from zones which will satisfy the caller's allocation
  * request.
  *
- * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
- * Because:
- * a) The caller may be trying to free *extra* pages to satisfy a higher-order
- *    allocation or
- * b) The target zone may be at high_wmark_pages(zone) but the lower zones
- *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
- *    zone defense algorithm.
- *
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.
  */
@@ -2568,6 +2560,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc,
 	unsigned long nr_soft_reclaimed;
 	unsigned long nr_soft_scanned;
 	gfp_t orig_mask;
+	pg_data_t *last_pgdat = NULL;
 
 	/*
 	 * If the number of buffer_heads in the machine exceeds the maximum
@@ -2580,11 +2573,18 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc,
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 					classzone_idx, sc->nodemask) {
-		if (!populated_zone(zone)) {
-			reclaim_idx--;
-			classzone_idx--;
+		BUG_ON(!populated_zone(zone));
+
+		/*
+		 * Shrink each node in the zonelist once. If the zonelist is
+		 * ordered by zone (not the default) then a node may be
+		 * shrunk multiple times but in that case the user prefers
+		 * lower zones being preserved
+		 */
+		if (zone->zone_pgdat == last_pgdat)
 			continue;
-		}
+		last_pgdat = zone->zone_pgdat;
+		reclaim_idx = zone_idx(zone);
 
 		/*
 		 * Take care memory controller reclaiming has small influence
-- 
2.6.4

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[RFC PATCH 00/27] Move LRU page reclaim from zones to nodes v2 Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 12/27] mm: vmscan: Do not reclaim from kswapd if there is any eligible zone Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 11/27] mm, vmscan: Clear congestion, dirty and need for compaction on a per-node basis Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 02/27] mm, vmscan: Check if cpusets are enabled during direct reclaim Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 08/27] mm, vmscan: Make kswapd reclaim in terms of nodes Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 13/27] mm, vmscan: Make shrink_node decisions more node-centric Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 09/27] mm, vmscan: Simplify the logic deciding whether kswapd sleeps Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 10/27] mm, vmscan: By default have direct reclaim only shrink once per node Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 04/27] mm, vmscan: Move lru_lock to the node Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 14:50 +0100
  [PATCH 14/27] mm, memcg: Move memcg limit enforcement from zones to nodes Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 15:00 +0100
  [PATCH 15/27] mm, workingset: Make working set detection node-aware Mel Gorman <mgorman@techsingularity.net> - 2016-02-23 15:00 +0100

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