From: Glauber Costa <glommer@parallels.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
Ying Han <yinghan@google.com>, Tejun Heo <htejun@gmail.com>,
Li Zefan <lizefan@huawei.com>
Subject: Re: [patch v2 3/6] memcg: rework mem_cgroup_iter to use cgroup iterators
Date: Wed, 28 Nov 2012 13:35:42 +0400 [thread overview]
Message-ID: <50B5DAEE.6060009@parallels.com> (raw)
In-Reply-To: <20121128093336.GD12309@dhcp22.suse.cz>
On 11/28/2012 01:33 PM, Michal Hocko wrote:
> On Wed 28-11-12 13:23:57, Glauber Costa wrote:
>> On 11/28/2012 01:17 PM, Michal Hocko wrote:
>>> On Wed 28-11-12 17:47:59, KAMEZAWA Hiroyuki wrote:
>>>> (2012/11/27 3:47), Michal Hocko wrote:
>>> [...]
>>>>> + /*
>>>>> + * Even if we found a group we have to make sure it is alive.
>>>>> + * css && !memcg means that the groups should be skipped and
>>>>> + * we should continue the tree walk.
>>>>> + * last_visited css is safe to use because it is protected by
>>>>> + * css_get and the tree walk is rcu safe.
>>>>> + */
>>>>> + if (css == &root->css || (css && css_tryget(css)))
>>>>> + memcg = mem_cgroup_from_css(css);
>>>>
>>>> Could you note that this iterator will never visit dangling(removed)
>>>> memcg, somewhere ?
>>>
>>> OK, I can add it to the function comment but the behavior hasn't changed
>>> so I wouldn't like to confuse anybody.
>>>
>>>> Hmm, I'm not sure but it may be trouble at shrkinking dangling
>>>> kmem_cache(slab).
>>>
>>> We do not shrink slab at all.
>>
>> yet. However...
>>
>>> Those objects that are in a dead memcg
>>> wait for their owner tho release them which will make the dangling group
>>> eventually go away
>>>
>>>>
>>>> Costa, how do you think ?
>>>>
>>
>> In general, I particularly believe it is a good idea to skip dead memcgs
>> in the iterator. I don't anticipate any problems with shrinking at all.
>
> We even cannot iterate dead ones because their cgroups are gone and so
> you do not have any way to iterate. So either make them alive by css_get
> or we cannot iterate them.
>
We are in full agreement.
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next prev parent reply other threads:[~2012-11-28 9:35 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-26 18:47 rework mem_cgroup iterator Michal Hocko
2012-11-26 18:47 ` [patch v2 1/6] memcg: synchronize per-zone iterator access by a spinlock Michal Hocko
2012-11-26 18:47 ` [patch v2 2/6] memcg: keep prev's css alive for the whole mem_cgroup_iter Michal Hocko
2012-11-28 8:38 ` Kamezawa Hiroyuki
2012-11-26 18:47 ` [patch v2 3/6] memcg: rework mem_cgroup_iter to use cgroup iterators Michal Hocko
2012-11-28 8:47 ` Kamezawa Hiroyuki
2012-11-28 9:17 ` Michal Hocko
2012-11-28 9:23 ` Glauber Costa
2012-11-28 9:33 ` Michal Hocko
2012-11-28 9:35 ` Glauber Costa [this message]
2012-11-30 4:07 ` Kamezawa Hiroyuki
2012-12-07 3:39 ` Ying Han
2012-12-07 3:43 ` Ying Han
2012-12-07 8:58 ` Michal Hocko
2012-12-07 17:12 ` Ying Han
2012-12-07 17:27 ` Michal Hocko
2012-12-07 19:16 ` Ying Han
2012-12-07 19:35 ` Michal Hocko
2012-12-07 9:01 ` Michal Hocko
2012-12-09 16:59 ` Ying Han
2012-12-11 15:50 ` Michal Hocko
2012-12-11 16:15 ` Michal Hocko
2012-12-11 18:10 ` Michal Hocko
2012-12-11 22:43 ` Ying Han
2012-12-12 8:55 ` Michal Hocko
2012-12-12 17:57 ` Ying Han
2012-12-12 18:08 ` Michal Hocko
2012-12-11 22:31 ` Ying Han
2012-12-09 19:39 ` Ying Han
2012-12-11 15:54 ` Michal Hocko
2012-12-11 22:36 ` Ying Han
2012-12-12 9:06 ` Michal Hocko
2012-12-12 18:09 ` Ying Han
2012-12-12 18:34 ` Michal Hocko
2012-12-12 18:42 ` Michal Hocko
2012-12-14 1:06 ` Ying Han
2012-12-14 10:56 ` [PATCH] memcg,vmscan: do not break out targeted reclaim without reclaimed pages Michal Hocko
2012-12-12 19:24 ` [patch v2 3/6] memcg: rework mem_cgroup_iter to use cgroup iterators Michal Hocko
2012-12-14 1:14 ` Ying Han
2012-12-14 12:07 ` Michal Hocko
2012-12-14 23:08 ` Ying Han
2012-12-14 12:37 ` Michal Hocko
2012-11-26 18:47 ` [patch v2 4/6] memcg: simplify mem_cgroup_iter Michal Hocko
2012-11-28 8:52 ` Kamezawa Hiroyuki
2012-11-30 4:09 ` Kamezawa Hiroyuki
2012-12-09 17:01 ` Ying Han
2012-12-11 15:57 ` Michal Hocko
2012-12-11 4:35 ` Ying Han
2012-12-11 16:01 ` Michal Hocko
2012-12-11 22:52 ` Ying Han
2012-11-26 18:47 ` [patch v2 5/6] memcg: further " Michal Hocko
2012-11-30 4:10 ` Kamezawa Hiroyuki
2012-11-30 9:08 ` Glauber Costa
2012-11-30 10:23 ` Michal Hocko
2012-11-26 18:47 ` [patch v2 6/6] cgroup: remove css_get_next Michal Hocko
2012-11-30 4:12 ` Kamezawa Hiroyuki
2012-11-30 8:18 ` Michal Hocko
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