From: Tejun Heo <tj@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>,
linux-mm@kvack.org, Oleg Nesterov <oleg@redhat.com>,
Vladimir Davydov <vdavydov@parallels.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 3/3] memcg: get rid of mm_struct::owner
Date: Thu, 28 May 2015 17:07:42 -0400 [thread overview]
Message-ID: <20150528210742.GF27479@htj.duckdns.org> (raw)
In-Reply-To: <20150526141011.GA11065@cmpxchg.org>
Hello, Johannes, Michal.
On Tue, May 26, 2015 at 10:10:11AM -0400, Johannes Weiner wrote:
> On Tue, May 26, 2015 at 01:50:06PM +0200, Michal Hocko wrote:
> > Please note that this patch introduces a USER VISIBLE CHANGE OF BEHAVIOR.
> > Without mm->owner _all_ tasks associated with the mm_struct would
> > initiate memcg migration while previously only owner of the mm_struct
> > could do that. The original behavior was awkward though because the user
> > task didn't have any means to find out the current owner (esp. after
> > mm_update_next_owner) so the migration behavior was not well defined
> > in general.
> > New cgroup API (unified hierarchy) will discontinue tasks file which
> > means that migrating threads will no longer be possible. In such a case
> > having CLONE_VM without CLONE_THREAD could emulate the thread behavior
> > but this patch prevents from isolating memcg controllers from others.
> > Nevertheless I am not convinced such a use case would really deserve
> > complications on the memcg code side.
>
> I think such a change is okay. The memcg semantics of moving threads
> with the same mm into separate groups have always been arbitrary. No
> reasonable behavior can be expected of this, so what sane real life
> usecase would rely on it?
I suppose that making mm always follow the threadgroup leader should
be fine, right? While this wouldn't make any difference in the
unified hierarchy, I think this would make more sense for traditional
hierarchies.
Thanks.
--
tejun
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next prev parent reply other threads:[~2015-05-28 21:07 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-26 11:50 [RFC 0/3] get rid of mm_struct::owner Michal Hocko
2015-05-26 11:50 ` [RFC 1/3] memcg: restructure mem_cgroup_can_attach() Michal Hocko
2015-05-26 11:50 ` [RFC 2/3] memcg: Use mc.moving_task as the indication for charge moving Michal Hocko
2015-05-26 11:50 ` [RFC 3/3] memcg: get rid of mm_struct::owner Michal Hocko
2015-05-26 14:10 ` Johannes Weiner
2015-05-26 15:11 ` Michal Hocko
2015-05-26 17:20 ` Johannes Weiner
2015-05-27 14:48 ` Michal Hocko
2015-05-28 21:07 ` Tejun Heo [this message]
2015-05-29 12:08 ` Michal Hocko
2015-05-29 13:10 ` Tejun Heo
2015-05-29 13:45 ` Michal Hocko
2015-05-29 14:07 ` Tejun Heo
2015-05-29 14:57 ` Michal Hocko
2015-05-29 15:23 ` Tejun Heo
2015-05-29 15:26 ` Michal Hocko
2015-05-26 16:36 ` Oleg Nesterov
2015-05-26 17:22 ` Michal Hocko
2015-05-26 17:38 ` Oleg Nesterov
2015-05-27 9:43 ` Michal Hocko
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