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

From: Vivek Kashyap
Date: Tue Aug 12 2008 - 23:47:30 EST


On Tue, 12 Aug 2008, Andrew Morton wrote:

On Mon, 11 Aug 2008 16:53:23 -0700
Matt Helsley <matthltc@xxxxxxxxxx> 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.
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Vivek Kashyap
Linux Technology Center, IBM
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