Hey, On Wed, Jun 05, 2013 at 10:36:28AM +0200, Michal Hocko wrote: > > It's still bound, no? Each live memcg can only keep limited number of > > cgroups cached, right? > > Assuming that they are cleaned up when the memcg is offlined then yes. Oh yeah, that's just me being forgetful. We definitely need to clean it up on offlining. > > Do you think that the number can actually grow harmful? Would you be > > kind enough to share some calculations with me? > > Well, each intermediate node might pin up-to NR_NODES * NR_ZONES * > NR_PRIORITY groups. You would need a big hierarchy to have chance to > cache different groups so that it starts matter. Yeah, NR_NODES can be pretty big. I'm still not sure whether this would be a problem in practice but yeah it can grow pretty big. > And do what? css_try_get to find out whether the cached memcg is still Hmmm? It can just look at the timestamp and if too old do cached = xchg(&iter->hint, NULL); if (cached) css_put(cached); > alive. Sorry, I do not like it at all. I find it much better to clean up > when the group is removed. Because doing things asynchronously just > makes it more obscure. There is no reason to do such a thing on the > background when we know _when_ to do the cleanup and that is definitely > _not a hot path_. Yeah, that's true. I just wanna avoid the barrier dancing. Only one of the ancestors can cache a memcg, right? Walking up the tree scanning for cached ones and putting them should work? Is that what you were suggesting? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
