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author | Wu Fengguang <fengguang.wu@intel.com> | 2009-09-22 04:03:11 +0400 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-22 18:17:39 +0400 |
commit | f86296317434b21585e229f6c49a33cb9ebab4d3 (patch) | |
tree | d4fb05d4aee1a8e373ec053e7316dc9847b2c417 /include/linux/mmzone.h | |
parent | 1a8670a29b5277cbe601f74ab63d2c5211fb3005 (diff) | |
download | linux-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.h | 6 |
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; |