Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-15 14:14:58]:

> On Thu, 15 Jan 2009 13:38:14 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> 
> > On Thu, 15 Jan 2009 11:14:20 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> > > > > > To handle the problem "parent may be obsolete",
> > > > > > 
> > > > > > call mem_cgroup_get(parent) at create()
> > > > > > call mem_cgroup_put(parent) at freeing memcg.
> > > > > >      (regardless of use_hierarchy.)
> > > > > > 
> > > > > > is clearer way to go, I think.
> > > > > > 
> > > > > > I wonder whether there is  mis-accounting problem or not..
> > > > > > 
> > hmm, after more consideration, although this patch can prevent the BUG,
> > it can leak memsw accounting of parents because memsw of parents, which
> > have been incremented by charge, does not decremented.
> > 
> > I'll try pet/put parent approach..
> > Or any other good ideas ?
> > 
> > 
> I believe get/put at create/destroy is enough now..
> Let's try and see what happens.
>

Other approach could be get_hierarchical/put_hierarchical, but that
can quickly get complex. Let us try and avoid it, unless nothing else
works.
 
-- 
	Balbir

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