* KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-08-03 12:21:58]: > On Tue, 3 Aug 2010 08:52:16 +0530 > Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-08-02 19:13:04]: > > > > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > > > Now, memory cgroup has an ID per cgroup and make use of it at > > > - hierarchy walk, > > > - swap recording. > > > > > > This patch is for making more use of it. The final purpose is > > > to replace page_cgroup->mem_cgroup's pointer to an unsigned short. > > > > > > This patch caches a pointer of memcg in an array. By this, we > > > don't have to call css_lookup() which requires radix-hash walk. > > > This saves some amount of memory footprint at lookup memcg via id. > > > > > > > It is a memory versus speed tradeoff, but if the number of created > > cgroups is low, it might not be all that slow, besides we do that for > > swap_cgroup anyway - no? > > > > In following patch, pc->page_cgroup is changed from pointer to ID. > Then, this lookup happens in lru_add/del, for example. > And, by this, we can place all lookup related things to __read_mostly. > With css_lookup(), we can't do it and have to be afraid of cache > behavior. > OK, fair enough > I hear there are a users who create 2000+ cgroups and considering > about "low number" user here is not important. > This patch is a help for getting _stable_ performance even when there are > many cgroups. > I've heard of one such user on the libcgroup mailing list. -- Three Cheers, Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>