linux-kernel - Re: [ckrm-tech] [PATCH 0/2] resource control file system

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Message-ID: <20070312150756.GB24742@in.ibm.com>
Date:	Mon, 12 Mar 2007 20:37:56 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	"Paul Menage" <menage@...gle.com>
Cc:	ckrm-tech@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	sam@...ain.net, dev@...ru, xemul@...ru, pj@....com,
	ebiederm@...ssion.com, winget@...gle.com,
	containers@...ts.osdl.org, "Serge E. Hallyn" <serue@...IBM.COM>,
	akpm@...ux-foundation.org
Subject: Re: [ckrm-tech] [PATCH 0/2] resource control file system - aka containers on top of nsproxy!

On Fri, Mar 09, 2007 at 02:09:35PM -0800, Paul Menage wrote:
> > 3. This next leads me to think that 'tasks' file in each directory doesnt make
> >    sense for containers. In fact it can lend itself to error situations (by
> >    administrator/script mistake) when some tasks of a container are in one
> >    resource class while others are in a different class.
> >
> >         Instead, from a containers pov, it may be usefull to write
> >         a 'container id' (if such a thing exists) into the tasks file
> >         which will move all the tasks of the container into
> >         the new resource class. This is the same requirement we
> >         discussed long back of moving all threads of a process into new
> >         resource class.
> 
> I think you need to give a more concrete example and use case of what
> you're trying to propose here. I don't really see what advantage
> you're getting.

Ok, this is what I had in mind:


	mount -t container -o ns /dev/namespace
	mount -t container -o cpu /dev/cpu

Lets we have the namespaces/resource-groups created as under:

	/dev/namespace
		    |-- prof
		    |	 |- tasks <- (T1, T2)
		    |    |- container_id <- 1 (doesnt exist today perhaps)
		    |
		    |-- student
		    |    |- tasks <- (T3, T4)
		    |    |- container_id <- 2 (doesnt exist today perhaps)

	/dev/cpu
	       |-- prof
	       |    |-- tasks
	       |    |-- cpu_limit (40%)
	       |
	       |-- student
	       |    |-- tasks
	       |    |-- cpu_limit (20%)
	       |
	       |


Is it possible to create the above structure in container patches? 
/me thinks so.

If so, then accidentally someone can do this:

	echo T1 > /dev/cpu/prof/tasks
	echo T2 > /dev/cpu/student/tasks

with the result that tasks of the same container are now in different
resource classes.

Thats why in case of containers I felt we shldnt allow individual tasks
to be cat'ed to tasks file. 

Or rather, it may be nice to say :

	echo "cid 2" > /dev/cpu/prof/tasks 

and have all tasks belonging to container id 2 move to the new resource
group.



-- 
Regards,
vatsa
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