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 <mgor...@suse.de>
---
 mm/vmscan.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4d7ddaf4f2f4..50aa650ac206 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2468,14 +2468,6 @@ 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.
  *
@@ -2490,6 +2482,7 @@ static bool shrink_zones(struct zonelist *zonelist, 
struct scan_control *sc,
        unsigned long nr_soft_scanned;
        gfp_t orig_mask;
        bool reclaimable = false;
+       pg_data_t *last_pgdat = NULL;
 
        /*
         * If the number of buffer_heads in the machine exceeds the maximum
@@ -2502,11 +2495,18 @@ static bool 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
-- 
2.3.5

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