linux-kernel - Re: [RFC][PATCH 1/6] memcg: free all at rmdir

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Date:	Thu, 13 Nov 2008 11:30:35 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, nishimura@....nes.nec.co.jp,
	menage@...gle.com
Subject: Re: [RFC][PATCH 1/6] memcg: free all at rmdir

On Thu, 13 Nov 2008 06:47:31 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> > btw, mem_cgroup_force_empty_list() uses PageLRU() outside ->lru_lock. 
> > That's racy, although afaict this race will only cause an accounting
> > error.
> > 
> > Or maybe not.  What happens if
> > __mem_cgroup_uncharge_common()->__mem_cgroup_remove_list() is passed a
> > page which isn't on an LRU any more?  boom?
> > 
> 
> IIRC, Kamezawa has been working on redoing force_empty interface. We are
> reworking its internals as well.
> 

PageLRU() is not used in account_move() version (in mmotm queue)
patches/memcg-move-all-acccounts-to-parent-at-rmdir.patch removes that.

We're now testing patch [6/6] which does

 1. remove per-memcg-lru-lock
 2. use zone->lru_lock instead of that.

Then, maintenance of this memcontrol.c will be much easier.

After patch [6/6]. account_move does

  isolate_page(page);
	move to other cgroup
  putback_lru_page(page);

as other usual routine does.

Thanks,
-Kame

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