Messages in this thread Patch in this message | | | Date | Mon, 1 Aug 2011 16:37:46 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH v4 3/5] memcg : stop scanning if enough |
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On Wed 27-07-11 14:49:00, KAMEZAWA Hiroyuki wrote: > memcg :avoid node fallback scan if possible. > > Now, try_to_free_pages() scans all zonelist because the page allocator > should visit all zonelists...but that behavior is harmful for memcg. > Memcg just scans memory because it hits limit...no memory shortage > in pased zonelist. > > For example, with following unbalanced nodes > > Node 0 Node 1 > File 1G 0 > Anon 200M 200M > > memcg will cause swap-out from Node1 at every vmscan. > > Another example, assume 1024 nodes system. > With 1024 node system, memcg will visit 1024 nodes > pages per vmscan... This is overkilling. > > This is why memcg's victim node selection logic doesn't work > as expected.
Previous patch adds nodemask filled by mem_cgroup_select_victim_node. Shouldn't we rather limit that nodemask to a victim node?
Or am I missing something?
The patch as is doesn't look nice it makes shrink_zones even more memcg-hacky: for_each_zone_zonelist_nodemask if (scanning_global_lru(sc)) /.../
shrink_zone(priority, zone, sc);
if (!scanning_global_lru(sc)) /.../
> > This patch is a help for stopping vmscan when we scanned enough. > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > --- > mm/vmscan.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > Index: mmotm-0710/mm/vmscan.c > =================================================================== > --- mmotm-0710.orig/mm/vmscan.c > +++ mmotm-0710/mm/vmscan.c > @@ -2058,6 +2058,16 @@ static void shrink_zones(int priority, s > } > > shrink_zone(priority, zone, sc); > + if (!scanning_global_lru(sc)) { > + /* > + * When we do scan for memcg's limit, it's bad to do > + * fallback into more node/zones because there is no > + * memory shortage. We quit as much as possible when > + * we reache target. > + */ > + if (sc->nr_to_reclaim <= sc->nr_reclaimed) > + break; > + } > } > } > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic
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