[PATCH] mm, vmscan: Make kswapd reclaim no more than needed

["Hillf Danton" <hillf.zj@alibaba-inc.com>]

We stop reclaiming pages if any eligible zone is balanced.

Signed-off-by: Hillf Danton <hillf.zj@alibaba-inc.com>
---

--- a/mm/vmscan.c	Thu Jun 23 17:56:34 2016
+++ b/mm/vmscan.c	Fri Jun 24 16:45:58 2016
@@ -3185,15 +3185,10 @@ static int balance_pgdat(pg_data_t *pgda
 			if (!populated_zone(zone))
 				continue;
 
-			if (!zone_balanced(zone, sc.order, classzone_idx)) {
-				classzone_idx = i;
-				break;
-			}
+			if (zone_balanced(zone, sc.order, classzone_idx))
+				goto out;
 		}
 
-		if (i < 0)
-			goto out;
-
 		/*
 		 * Do some background aging of the anon list, to give
 		 * pages a chance to be referenced before reclaiming. All
@@ -3236,19 +3231,6 @@ static int balance_pgdat(pg_data_t *pgda
 		/* Check if kswapd should be suspending */
 		if (try_to_freeze() || kthread_should_stop())
 			break;
-
-		/*
-		 * Stop reclaiming if any eligible zone is balanced and clear
-		 * node writeback or congested.
-		 */
-		for (i = 0; i <= classzone_idx; i++) {
-			zone = pgdat->node_zones + i;
-			if (!populated_zone(zone))
-				continue;
-
-			if (zone_balanced(zone, sc.order, classzone_idx))
-				goto out;
-		}
 
 		/*
 		 * Raise priority if scanning rate is too low or there was no
--

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