Re: [PATCH v2 2/5] memcg: provide root figures from system totals

[Glauber Costa <glommer@parallels.com>]

On 03/19/2013 04:46 PM, 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?
> The patch aims at reducing an overhead when there there are no other
> groups, right?
> 
You've already noted yourself that this is done in a later patch.

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