On Wed 20-03-13 12:34:01, Glauber Costa wrote: > On 03/20/2013 12:18 PM, Michal Hocko wrote: > > On Wed 20-03-13 12:08:17, Glauber Costa wrote: > >> On 03/20/2013 12:03 PM, Michal Hocko wrote: > >>> On Wed 20-03-13 11:03:17, Glauber Costa wrote: > >>>> 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. > >>> > >>> If you simply switch to accounting for root then you do not have to care > >>> about this, don't you? > >>> > >> Of course not, but the whole point here is *not* accounting root. > > > > I thought the objective was to not account root if there are no > > children. > > It is the goal, yes. As I said: I want the root-only case to keep > providing userspace with meaningful statistics, Sure, statistics need to stay at the place. I am not objecting on that. > therefore the bypass. I am just arguing about bypassing root even when there are children and use_hierarchy == 1 because it adds more code to maintain. > But since the machinery is in place, it is trivial to keep bypassing for > use_hierarchy = 1 at the root level. If you believe it would be simpler, > I could refrain from doing it. I am all for "the simple the better" and add more optimizations on top. We have a real issue now and we should eliminate it. My original plan was to look at the bottlenecks and eliminate them one after another in smaller steps. But all the work I have on the plate is preempting me from looking into that... -- Michal Hocko 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>