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. I would see the "not account root at all" as another step. And we are skipping charging it already (do not call mem_cgroup_do_charge) for root. > So if we are entirely skipping root account, it, I personally believe > we need to replace it with something else so we can keep things > working as much as we can. > > It doesn't need to be perfect, though: There is no way we can have > max_usage without something like a res_counter that locks memory > charges. I believe we can live without that. But as for the basic > statistics and numbers, I believe they should keep working. [...] -- 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>