Messages in this thread | | | Date | Fri, 21 Aug 2009 19:57:24 +0900 | Subject | Re: [PATCH -v2 changelog updated] mm: do batched scans for mem_cgroup | From | KOSAKI Motohiro <> |
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2009/8/21 Wu Fengguang <fengguang.wu@intel.com>: > 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. >
Looks good to me. Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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