On Wed, Jul 23, 2014 at 07:44:49AM -0400, Johannes Weiner wrote: > On Wed, Jul 23, 2014 at 12:24:15PM +0100, Mel Gorman wrote: > > When updating memcg VM statistics like PGFAULT we take the rcu read > > lock and lookup the memcg. For statistic updates this is overkill > > when the process may not belong to a memcg. This patch adds a light > > check to check if a memcg potentially exists. It's race-prone in that > > some VM stats may be missed when a process first joins a memcg but > > that is not serious enough to justify a constant performance penalty. > > Tasks always belong to a memcg, the root group per default. There > isn't really any accounting that could be omitted. > Crap, ok, I had not taken that into account. The lookup of that cannot really be avoided. It's a pity because the stats on the root memcg are not likely to be that interesting. Thanks for reviewing. -- 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>