[PATCH 4/6] mm: kswapd: Reset kswapd_max_order and classzone_idx after reading

[Mel Gorman]

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@xxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/vmscan.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4d968b0..e1be4e8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2646,6 +2646,8 @@ 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();
-- 
1.7.1

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