mm: kswapd: treat zone->all_unreclaimable in sleeping_prematurely similar to balance_pgdat()

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@csn.ul.ie>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Simon Kirby <sim@hostway.ca>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index dafb9d91b604..388a0447b8e8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2244,8 +2244,16 @@ 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_safe(zone, order, high_wmark_pages(zone),
                                                                 0, 0))