Messages in this thread | | | Date | Fri, 21 Aug 2009 12:55:27 +0900 | Subject | Re: [PATCH -v2] mm: do batched scans for mem_cgroup | From | Minchan Kim <> |
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On Thu, Aug 20, 2009 at 1:05 PM, Wu Fengguang<fengguang.wu@intel.com> wrote: > On Thu, Aug 20, 2009 at 11:13:47AM +0800, KAMEZAWA Hiroyuki wrote: >> On Thu, 20 Aug 2009 10:49:29 +0800 >> Wu Fengguang <fengguang.wu@intel.com> wrote: >> >> > 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, it will be scanned SWAP_CLUSTER_MAX=32 pages in effect. >> > >> > 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. >> > >> > This batching won't blur up the cgroup limits, since it is driven by >> > "pages reclaimed" rather than "pages scanned". When shrink_zone() >> > decides to cancel (and save) one smallish scan, it may well be called >> > again to accumulate up nr_saved_scan. >> > >> > It could possibly be a problem for some tiny mem_cgroup (which may be >> > _full_ scanned too much times in order to accumulate up nr_saved_scan). >> > >> > CC: Rik van Riel <riel@redhat.com> >> > CC: Minchan Kim <minchan.kim@gmail.com> >> > CC: Balbir Singh <balbir@linux.vnet.ibm.com> >> > CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> >> > CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> >> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
It looks better than now :)
I hope you will rewrite description and add test result in changelog. :) Thanks for your great effort.
-- Kind regards, Minchan Kim -- 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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