[Devel] Re: [PATCH v3 06/13] memcg: kmem controller infrastructure

[Glauber Costa]

On 09/30/2012 12:25 PM, Tejun Heo wrote:
> On Fri, Sep 28, 2012 at 03:34:19PM +0400, Glauber Costa wrote:
>> On 09/27/2012 05:44 PM, Michal Hocko wrote:
>>> Anyway, I have just noticed that __mem_cgroup_try_charge does
>>> VM_BUG_ON(css_is_removed(&memcg->css)) on a given memcg so you should
>>> keep css ref count up as well.
>>
>> IIRC, css_get will prevent the cgroup directory from being removed.
>> Because some allocations are expected to outlive the cgroup, we
>> specifically don't want that.
> 
> That synchronous ref draining is going away.  Maybe we can do that
> before kmemcg?  Michal, do you have some timeframe on mind?
> 

Since you said yourself in other points in this thread that you are fine
with some page references outliving the cgroup in the case of slab, this
is a situation that comes with the code, not a situation that was
incidentally there, and we're making use of.