On 03/19/2013 04:55 PM, Michal Hocko wrote: > On Tue 19-03-13 13:46:50, Michal Hocko wrote: >> On Tue 05-03-13 17:10:55, Glauber Costa wrote: >>> For the root memcg, there is no need to rely on the res_counters if hierarchy >>> is enabled The sum of all mem cgroups plus the tasks in root itself, is >>> necessarily the amount of memory used for the whole system. Since those figures >>> are already kept somewhere anyway, we can just return them here, without too >>> much hassle. >>> >>> Limit and soft limit can't be set for the root cgroup, so they are left at >>> RESOURCE_MAX. Failcnt is left at 0, because its actual meaning is how many >>> times we failed allocations due to the limit being hit. We will fail >>> allocations in the root cgroup, but the limit will never the reason. >> >> I do not like this very much to be honest. It just adds more hackery... >> Why cannot we simply not account if nr_cgroups == 1 and move relevant >> global counters to the root at the moment when a first group is >> created? > > OK, it seems that the very next patch does what I was looking for. So > why all the churn in this patch? > Why do you want to make root even more special? Because I am operating under the assumption that we want to handle that transparently and keep things working. If you tell me: "Hey, reading memory.usage_in_bytes from root should return 0!", then I can get rid of that. The fact that I keep bypassing when hierarchy is present, it is more of a reuse of the infrastructure since it's there anyway. Also, I would like the root memcg to be usable, albeit cheap, for projects like memory pressure notifications. -- 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
