Date:	Mon, 12 Dec 2011 09:31:16 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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>,
	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 Sun, 11 Dec 2011 15:50:56 +0100
Glauber Costa <glommer@...allels.com> wrote:

> On 12/09/2011 03:55 PM, Glauber Costa wrote:
> > On 12/09/2011 12:03 PM, Peter Zijlstra wrote:
> >> On Mon, 2011-12-05 at 07:32 -0200, Glauber Costa wrote:
> >>> Hi,
> >>>
> >>> Specially Peter and Paul, but all the others:
> >>>
> >>> As you can see in https://lkml.org/lkml/2011/12/4/178, and in my answer
> >>> to that, there is a question - one I've asked before but without that
> >>> much of an audience - of whether /proc files read from process living on
> >>> cgroups should display global or per-cgroup resources.
> >>>
> >>> In the past, I was arguing for a knob to control that, but I recently
> >>> started to believe that a knob here will only overcomplicate matters:
> >>> if you live in a cgroup, you should display only the resources you can
> >>> possibly use. Global is for whoever is in the main cgroup.
> >>>
> >>> Now, it comes two questions:
> >>> 1) Do you agree with that, for files like /proc/stat ? I think the most
> >>> important part is to be consistent inside the system, regardless of what
> >>> is done
> >>
> >> Personally I don't give a rats arse about (/proc vs) cgroups :-)
> >> Currently /proc is unaffected by whatever cgroup you happen to be in and
> >> that seems to make some sort of sense.
> >>
> >> 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 ?
> >
> >
> >> IOW a /proc namespace coupled to cgroup scope would do what you want.
> >> Now my head hurts..
> >
> > Mine too. The idea is good, but too broad. Boils down to: How do you
> > couple them? And none of the methods I thought about seemed to make any
> > sense.
> >
> > If we really want to have the values in /proc being opted-in, I think
> > Kamezawa's idea of a mount option is the winner so far.
> >
> 
> Ok:
> 
> How about the following patch to achieve this ?

Hmm, What I thought was mount option for procfs. Containers will mount its own
/proc file systems. Do you have any pros. / cons. ?
IIUC, cgroup can be mounted per subsystems. Then, options can be passed per
subsystems. It's a mess but we don't need to bring this to procfs.

How about

  # mount -t procfs proc /container_root/proc -o cgroup_aware

to show cgroup aware procfs ? I think this will be easy to be used with
namespace/chroot, etc.

Thanks,
-Kame


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