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

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Message-ID: <alpine.DEB.2.00.1205302314190.25774@chino.kir.corp.google.com>
Date:	Wed, 30 May 2012 23:17:51 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	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

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.
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