On Tue, Mar 19, 2013 at 06:16:50PM +0800, Simon Jeons wrote: > Hi Mel, > On 03/19/2013 05:55 PM, Mel Gorman wrote: > >On Tue, Mar 19, 2013 at 07:53:16AM +0800, Simon Jeons wrote: > >>Hi Mel, > >>On 03/17/2013 09:04 PM, Mel Gorman wrote: > >>>The number of pages kswapd can reclaim is bound by the number of pages it > >>>scans which is related to the size of the zone and the scanning priority. In > >>>many cases the priority remains low because it's reset every SWAP_CLUSTER_MAX > >>>reclaimed pages but in the event kswapd scans a large number of pages it > >>>cannot reclaim, it will raise the priority and potentially discard a large > >>>percentage of the zone as sc->nr_to_reclaim is ULONG_MAX. The user-visible > >>>effect is a reclaim "spike" where a large percentage of memory is suddenly > >>>freed. It would be bad enough if this was just unused memory but because > >>Since there is nr_reclaimed >= nr_to_reclaim check if priority is > >>large than DEF_PRIORITY in shrink_lruvec, how can a large percentage > >>of memory is suddenly freed happen? > >> > >Because of the priority checks made in get_scan_count(). Patch 5 has > >more detail on why this happens. > > > But nr_reclaim >= nr_to_reclaim check in function shrink_lruvec is > after scan each evictable lru, so if priority == 0, still scan the > whole world. > Patch 5 deals with the case where priority == 0. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>