linux-kernel - Re: [PATCH] meminfo: show /proc/meminfo base on container's memcg

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Date:	Thu, 31 May 2012 02:23:26 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Gao feng <gaofeng@...fujitsu.com>, hannes@...xchg.org,
	mhocko@...e.cz, bsingharora@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, containers@...ts.linux-foundation.org
Subject: Re: [PATCH] meminfo: show /proc/meminfo base on container's memcg

(5/31/12 2:17 AM), David Rientjes wrote:
> On Thu, 31 May 2012, Kamezawa Hiroyuki wrote:
>
>>> The bottomline is that /proc/meminfo is one of many global resource state
>>> interfaces and doesn't imply that every thread has access to the full
>>> resources.  It never has.  It's very simple for another thread to consume
>>> a large amount of memory as soon as your read() of /proc/meminfo completes
>>> and then that information is completely bogus.
>>
>> Why you need to discuss this here ? We know all information are snapshot.
>>
>
> MemTotal is usually assumed to be static from /proc/meminfo and could now
> change radically without notification to the application.
>
>> Hmm....maybe need to mount cgroup in the container (again) and get an access
>> to cgroup
>> hierarchy and find the cgroup it belongs to......if it's allowed.
>
> An application should always know the cgroup that its attached to and be
> able to read its state using the command that I gave earlier.

No. you don't need why userland folks want namespaces. Even though you don't
need namespaces. It doesn't good reason to refuse another use case.

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