On 03/20/2013 12:58 PM, Michal Hocko wrote: > 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... > Been there, done that =) I have no objections removing the special case for use_hierarchy == 1. -- 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>