From mboxrd@z Thu Jan  1 00:00:00 1970
From: KOSAKI Motohiro <kosaki.motohiro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH] meminfo: show /proc/meminfo base on container's memcg
Date: Thu, 31 May 2012 02:23:26 -0400
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To: David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mhocko-AlSwsSmVLrQ@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, KOSAKI Motohiro <kosaki.motohiro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
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(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.