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. 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. >> 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. > > root memcg without any childre, right? > yes, of course. -- 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>