mm: kswapd: reset kswapd_max_order and classzone_idx after reading

When kswapd wakes up, it reads its order and classzone from pgdat and
calls balance_pgdat.  While its awake, it potentially reclaimes at a high
order and a low classzone index.  This might have been a once-off that was
not required by subsequent callers.  However, because the pgdat values
were not reset, they remain artifically high while balance_pgdat() is
running and potentially kswapd enters a second unnecessary reclaim cycle.
Reset the pgdat order and classzone index after reading.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
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, 2 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 46711f080f38..dafb9d91b604 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2653,6 +2653,8 @@ static int kswapd(void *p)
                         kswapd_try_to_sleep(pgdat, order);
                         order = pgdat->kswapd_max_order;
                         classzone_idx = pgdat->classzone_idx;
+                        pgdat->kswapd_max_order = 0;
+                        pgdat->classzone_idx = MAX_NR_ZONES - 1;
                 }
 
                 ret = try_to_freeze();