[PATCH 5/6] mm: kswapd: Treat zone->all_unreclaimable in sleeping_prematurely similar to balance_pgdat()

[Mel Gorman]

After DEF_PRIORITY, balance_pgdat() considers all_unreclaimable zones to
be balanced but sleeping_prematurely does not. This can force kswapd to
stay awake longer than it should. This patch fixes it.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---
 mm/vmscan.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bc233d8..d7b0a3c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2149,8 +2149,16 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
 		if (!populated_zone(zone))
 			continue;
 
-		if (zone->all_unreclaimable)
+		/*
+		 * balance_pgdat() skips over all_unreclaimable after
+		 * DEF_PRIORITY. Effectively, it considers them balanced so
+		 * they must be considered balanced here as well if kswapd
+		 * is to sleep
+		 */
+		if (zone->all_unreclaimable) {
+			balanced += zone->present_pages;
 			continue;
+		}
 
 		if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
 								0, 0))
-- 
1.7.1

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