linux-kernel - Re: [-mm] Add an owner to the mm

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Date:	Fri, 04 Apr 2008 00:18:11 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Paul Menage <menage@...gle.com>
CC:	Pavel Emelianov <xemul@...nvz.org>,
	Hugh Dickins <hugh@...itas.com>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, taka@...inux.co.jp,
	linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [-mm] Add an owner to the mm_struct (v7)

Paul Menage wrote:
> On Thu, Apr 3, 2008 at 11:34 AM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
>>  That is indeed quite bad. Do we have to retire the group_leader to init_css_set?
>>  Can we not check for delay_group_leader() there?
>>
> 
> That might have unintentded consequences, such as leaving a pid in the
> cgroup that can't be moved (since it's PF_EXITING) but won't go away
> until its threads have all exited.
> Maybe that's OK if the other threads are guaranteed to have started
> exiting by this point. We'd need some cleanup for when the group
> leader finally did exit.

Yes, we might be stuck with an unremovable group, but I am not sure how to
address the side-effect at this point. Not having that check could mean that
mm_update_new_owner() will be called very frequently and for thousands of
threads that could clearly become an overhead, if threads start exiting one by
one - lead by the thread group leader.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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