path: root/mm/page_alloc.c
diff options
authorWu Fengguang <>2009-09-21 17:03:11 -0700
committerLinus Torvalds <>2009-09-22 07:17:39 -0700
commitf86296317434b21585e229f6c49a33cb9ebab4d3 (patch)
treed4fb05d4aee1a8e373ec053e7316dc9847b2c417 /mm/page_alloc.c
parent1a8670a29b5277cbe601f74ab63d2c5211fb3005 (diff)
mm: do batched scans for mem_cgroup
For mem_cgroup, shrink_zone() may call shrink_list() with nr_to_scan=1, in which case shrink_list() _still_ calls isolate_pages() with the much larger SWAP_CLUSTER_MAX. It effectively scales up the inactive list scan rate by up to 32 times. For example, with 16k inactive pages and DEF_PRIORITY=12, (16k >> 12)=4. So when shrink_zone() expects to scan 4 pages in the active/inactive list, the active list will be scanned 4 pages, while the inactive list will be (over) scanned SWAP_CLUSTER_MAX=32 pages in effect. And that could break the balance between the two lists. It can further impact the scan of anon active list, due to the anon active/inactive ratio rebalance logic in balance_pgdat()/shrink_zone(): inactive anon list over scanned => inactive_anon_is_low() == TRUE => shrink_active_list() => active anon list over scanned So the end result may be - anon inactive => over scanned - anon active => over scanned (maybe not as much) - file inactive => over scanned - file active => under scanned (relatively) The accesses to nr_saved_scan are not lock protected and so not 100% accurate, however we can tolerate small errors and the resulted small imbalanced scan rates between zones. Cc: Rik van Riel <> Reviewed-by: KOSAKI Motohiro <> Acked-by: Balbir Singh <> Reviewed-by: Minchan Kim <> Signed-off-by: KAMEZAWA Hiroyuki <> Signed-off-by: Wu Fengguang <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/page_alloc.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 770f011e1c1..84d9da1e8f4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3809,7 +3809,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
for_each_lru(l) {
- zone->lru[l].nr_saved_scan = 0;
+ zone->reclaim_stat.nr_saved_scan[l] = 0;
zone->reclaim_stat.recent_rotated[0] = 0;
zone->reclaim_stat.recent_rotated[1] = 0;