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

[Hillf Danton]

We stop reclaiming pages if any eligible zone is balanced.

Signed-off-by: Hillf Danton <hillf...@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
--