Re: [PATCH 0/9] OpenVZ kernel based checkpointing/restart

Oren Laadan
2008-09-04T08:14:57Z

Andrey Mirkin wrote:
> This patchset introduces kernel based checkpointing/restart as it is
> implemented in OpenVZ project. This patchset has limited functionality and
> are able to checkpoint/restart only single process. Recently Oren Laaden
> sent another kernel based implementation of checkpoint/restart. The main
> differences between this patchset and Oren's patchset are:

Thanks Andrey. I'll take a close look at it by the weekend. Just a couple
of comments after a very brief look at the code:

>
> * In this patchset checkpointing initiated not from the process
> (right now we do not have a container, only namespaces), Oren's patchset
> performs checkpointing from the process context.

Actually, my patch is written to checkpoint from outside the context of the
target task; for simplicity only, it is applied to the current process.

>
> * Restart in this patchset is initiated from process, which restarts a new
> process (in new namespaces) with saved state. Oren's patchset uses the same
> process from which restart was initiated and restore saved state over it.

Here, too, handling of namespaces was left out in order to provide a simple
proof of concept. In fact, spawning a new process and entering a new namespace
can be easily done in user-space.

Oren.

>
> * Checkpoint/restart functionality in this patchset is implemented as a kernel
> module
>
>
> As checkpointing is initiated not from the process which state should be saved
> we should freeze a process before saving its state. Right now Container Freezer
> from Matt Helsley can be used for this.
>
> This patchset introduce only a concept how kernel based checkpointing/restart
> can be implemented and are able to checkpoint/restart only a single process
> with simple VMAs.
>
> I've tried to split my patchset in small patches to make review more easier.
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