Re: [RFC][PATCH 2/2] memcg: hardwall hierarhcy for memcg

[Daisuke Nishimura]

> > > @@ -1096,6 +1238,12 @@ static void mem_cgroup_destroy(struct cg
> > >        int node;
> > >        struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> > >
> > > +       if (cont->parent &&
> > > +           mem->hierarchy_model == MEMCG_HARDWALL_HIERARCHY) {
> > > +               /* we did what we can...just returns what we borrow */
> > > +               res_counter_return_resource(&mem->res, -1, NULL, 0);
> > > +       }
> > > +
> > 
> > Should we also re-account any remaining child usage to the parent?
> > 
> When this is called, there are no process in this group. Then, remaining
> resources in this level is
>   - file cache
>   - swap cache (if shared)
>   - shmem
> 
> And the biggest usage will be "file cache".
> So, I don't think it's necessary to move child's usage to the parent,
> in hurry. But maybe shmem is worth to be moved.
> 
> I'd like to revisit this when I implements "usage move at task move"
> logic. (currenty, memory usage doesn't move to new cgroup at task_attach.)
> 
> It will help me to implement the logic "move remaining usage to the parent"
> in clean way.
> 

I agree that "usage move at task move" is needed before
"move remaining usage to the parent".


Thanks,
Daisuke Nishimura.
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