linux-kernel - Re: [linux-pm] [PATCH 0/5] Container Freezer v6: Reuse Suspend Freezer

Open Source and information security mailing list archives

Date:	Tue, 12 Aug 2008 20:47:10 -0700 (Pacific Daylight Time)
From:	Vivek Kashyap <kashyapv@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Matt Helsley <matthltc@...ibm.com>,
	containers@...ts.linux-foundation.org, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, menage@...gle.com,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [linux-pm] [PATCH 0/5] Container Freezer v6: Reuse Suspend
 Freezer

On Tue, 12 Aug 2008, Andrew Morton wrote:

> On Mon, 11 Aug 2008 16:53:23 -0700
> Matt Helsley <matthltc@...ibm.com> wrote:
>
>> This patch series introduces a cgroup subsystem that utilizes the swsusp
>> freezer to freeze a group of tasks. It's immediately useful for batch job
>> management scripts. It should also be useful in the future for implementing
>> container checkpoint/restart.
>
> I don't think that this provides anything like sufficient detail to justify
> merging a whole bunch of stuff into Linux.
>
> What does "It's immediately useful for batch job management scripts."
> mean?  How is it useful?  Examples?  Why would an operator want this
> feature, and how would it be used?  _much_ more information is needed!

A batch-manager/job scheduler (such as loadleveler) must at times stop all 
tasks associated with a workload being run in a container. The workload may 
constitute of multiple tasks - some of which are in different sessions. 
A signal (STOP/CONT) to the Containers 'init' wont be transmitted to all 
the tasks in the Container. The 'freezer' mechanism allows this control
to be implemented in a clean way.

Vivek
>
> Once we've actually found out what this work is useful for, we can move
> onto identification of and discussion of alternatives.  One would be "why not
> use plain old SIGSTOP?"  Another alternative is, of course "that's not useful
> enough to justify merging the code".  But we don't know yet, coz you didn't
> tell us.
> _______________________________________________
> linux-pm mailing list
> linux-pm@...ts.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/linux-pm
>

__

Vivek Kashyap
Linux Technology Center, IBM
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