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authorWu Fengguang <fengguang.wu@intel.com>2009-09-22 04:03:11 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 18:17:39 +0400
commitf86296317434b21585e229f6c49a33cb9ebab4d3 (patch)
treed4fb05d4aee1a8e373ec053e7316dc9847b2c417 /include/linux/mmzone.h
parent1a8670a29b5277cbe601f74ab63d2c5211fb3005 (diff)
downloadlinux-f86296317434b21585e229f6c49a33cb9ebab4d3.tar.xz
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 <riel@redhat.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mmzone.h')
-rw-r--r--include/linux/mmzone.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9c50309b30a1..c188ea624c74 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -273,6 +273,11 @@ struct zone_reclaim_stat {
*/
unsigned long recent_rotated[2];
unsigned long recent_scanned[2];
+
+ /*
+ * accumulated for batching
+ */
+ unsigned long nr_saved_scan[NR_LRU_LISTS];
};
struct zone {
@@ -327,7 +332,6 @@ struct zone {
spinlock_t lru_lock;
struct zone_lru {
struct list_head list;
- unsigned long nr_saved_scan; /* accumulated for batching */
} lru[NR_LRU_LISTS];
struct zone_reclaim_stat reclaim_stat;