linux-kernel - Re: How to draw values for /proc/stat

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Date:	Mon, 12 Dec 2011 10:33:33 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Glauber Costa <glommer@...allels.com>
Cc:	Paul Turner <pjt@...gle.com>, cgroups@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>, devel@...nvz.org,
	Linux Containers <containers@...ts.osdl.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: How to draw values for /proc/stat

On Fri, 2011-12-09 at 12:55 -0200, Glauber Costa wrote:
> On 12/09/2011 12:03 PM, Peter Zijlstra wrote:

> > Namespaces seem to be about limiting visibility, cgroups about
> > controlling resources.
> >
> > The two things are hopelessly disjoint atm, but I believe someone was
> > looking at this mess.
> 
> I did take a look at this (if anyone else was, I'd like to know so we 
> can share some ideas), but I am not convinced we should do anything to 
> join them anymore. We virtualization people are to the best of my 
> knowledge the only ones doing namespaces. Cgroups, OTOH, got a lot bigger.
> 
> What I am mostly concerned about now, is how consistent they will be.
> /proc always being always global indeed does make sense, but my question 
> still stands: if you live in a resource-controlled world, why should you 
> even see resources you will never own ?

Since without namespaces you can still see the rest of the world. So it
makes sense to me to still see all resources too.

Also, proportional controllers might not see a consistent slice of the
resource, making the stats rather awkward to interpret.

Furthermore, not everybody might care about these statistics at all and
I know pjt objected to being subjected to the extra accounting (pjt do
speak up etc..).

> If it is not co-mounted, we draw the global value. If you don't mount 
> it, I someone does not mount it, I can assure you he doesn't care about 
> it. We for sure will.

Anyway, looking at the rest of the emails in this thread the current
proposal is a cgroup mount option that indicates if you want these
per-cgroup stats or not, right?
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