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, therefore the bypass. 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. -- 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>