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Subject[PATCH 09/31] mm, vmscan: by default have direct reclaim only shrink once per node
Date
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>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/vmscan.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b524d3b72527..34656173a670 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2552,14 +2552,6 @@ static inline bool compaction_ready(struct zone *zone, int order, int classzone_
* 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.
*/
@@ -2571,6 +2563,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
unsigned long nr_soft_scanned;
gfp_t orig_mask;
enum zone_type classzone_idx;
+ pg_data_t *last_pgdat = NULL;

/*
* If the number of buffer_heads in the machine exceeds the maximum
@@ -2600,6 +2593,16 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
classzone_idx--;

/*
+ * 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;
+
+ /*
* Take care memory controller reclaiming has small influence
* to global LRU.
*/
--
2.6.4
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