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[PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone

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kswapd is woken when zones are below the low watermark but the wakeup
decision is not taking the classzone into account.  Now that reclaim is
node-based, it is only required to wake kswapd once per node and only if
all zones are unbalanced for the requested classzone.

Note that one node might be checked multiple times but there is no cheap
way of tracking what nodes have already been visited for zoneslists that
be ordered by either zone or node.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/vmscan.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7a2d69612231..b9cff9047ac0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3389,6 +3389,7 @@ static int kswapd(void *p)
 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
 {
 	pg_data_t *pgdat;
+	int z;
 
 	if (!populated_zone(zone))
 		return;
@@ -3402,8 +3403,16 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
 	pgdat->kswapd_order = max(pgdat->kswapd_order, order);
 	if (!waitqueue_active(&pgdat->kswapd_wait))
 		return;
-	if (zone_balanced(zone, order, 0))
-		return;
+
+	/* Only wake kswapd if all zones are unbalanced */
+	for (z = 0; z <= classzone_idx; z++) {
+		zone = pgdat->node_zones + z;
+		if (!populated_zone(zone))
+			continue;
+
+		if (zone_balanced(zone, order, classzone_idx))
+			return;
+	}
 
 	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
 	wake_up_interruptible(&pgdat->kswapd_wait);
-- 
2.6.4

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[PATCH 00/27] Move LRU page reclaim from zones to nodes v6 Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 25/27] mm: page_alloc: Cache the last node whose dirty limit is reached Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 07/27] mm, vmscan: Remove balance gap Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 02/27] mm, vmscan: Move lru_lock to the node Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
    Re: [PATCH 02/27] mm, vmscan: Move lru_lock to the node Vlastimil Babka <vbabka@suse.cz> - 2016-06-10 18:40 +0200
      Re: [PATCH 02/27] mm, vmscan: Move lru_lock to the node Peter Zijlstra <peterz@infradead.org> - 2016-06-10 19:50 +0200
  [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 18/27] mm: Move most file-based accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 17/27] mm: Rename NR_ANON_PAGES to NR_ANON_MAPPED Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 23/27] mm, vmscan: Add classzone information to tracepoints Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 10/27] mm, vmscan: Clear congestion, dirty and need for compaction on a per-node basis Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 08/27] mm, vmscan: Simplify the logic deciding whether kswapd sleeps Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 20/27] mm, vmscan: Update classzone_idx if buffer_heads_over_limit Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 27/27] mm: vmstat: Account per-zone stalls and pages skipped during reclaim Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 01/27] mm, vmstat: Add infrastructure for per-node vmstats Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
    Re: [PATCH 01/27] mm, vmstat: Add infrastructure for per-node vmstats Vlastimil Babka <vbabka@suse.cz> - 2016-06-10 15:40 +0200
      Re: [PATCH 01/27] mm, vmstat: Add infrastructure for per-node vmstats Mel Gorman <mgorman@techsingularity.net> - 2016-06-10 15:50 +0200
  [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 04/27] mm, vmscan: Begin reclaiming pages on a per-node basis Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 19/27] mm: Move vmscan writes and file write accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 12/27] mm, vmscan: Make shrink_node decisions more node-centric Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:10 +0200
  [PATCH 16/27] mm: Move page mapped accounting to the node Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 22/27] mm: Convert zone_reclaim to node_reclaim Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 09/27] mm, vmscan: By default have direct reclaim only shrink once per node Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 14/27] mm, workingset: Make working set detection node-aware Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 24/27] mm, page_alloc: Remove fair zone allocation policy Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 13/27] mm, memcg: Move memcg limit enforcement from zones to nodes Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:20 +0200
  [PATCH 26/27] mm: vmstat: Replace __count_zone_vm_events with a zone id equivalent Mel Gorman <mgorman@techsingularity.net> - 2016-06-09 20:30 +0200
  Re: [PATCH 03/27] mm, vmscan: Move LRU lists to node Vlastimil Babka <vbabka@suse.cz> - 2016-06-10 20:10 +0200

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