linux-kernel - Re: [PATCH 9/12] memcg allocate all page

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Date:	Wed, 1 Oct 2008 15:17:34 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"xemul@...nvz.org" <xemul@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Hansen <haveblue@...ibm.com>, ryov@...inux.co.jp
Subject: Re: [PATCH 9/12] memcg allocate all page_cgroup at boot

On Wed, 01 Oct 2008 11:29:04 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > __mem_cgroup_move_lists() will have some amount of changes. And we should
> > check dead lock again.
> 
> __mem_cgroup_move_lists() is called from mem_cgroup_isolate_pages() and
> mem_cgroup_move_lists(). In mem_cgroup_move_lists(), we have the page_cgroup
> lock. I think the current code works on the assumption (although not documented
> anywhere I've seen), that PAGE_CGROUP_FLAG_INACTIVE/ACTIVE/UNEVICTABLE bits are
> protected by lru_lock. Please look at
yes, I wrote them.

> 
> __mem_cgroup_remove_list
> __mem_cgroup_add_list
> __mem_cgroup_move_lists
> __mem_cgroup_charge_common (sets this flag, before the pc is associated with the
> page).
> 
But my point is lru_lock doesn't means page_cgroup is not locked by someone and
we must take always lock_page_cgroup() when we modify flags.

Then, mem_cgroup_isolate_page() should have to take lock.
But this means we have to care preemption for avoiding deadlock.
Maybe need some time to test.

Thanks,
-Kame

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