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

Cedric Le Goater
2008-09-03T12:28:54Z

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:
>
> * 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.
>
> * 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.
>
> * Checkpoint/restart functionality in this patchset is implemented as a kernel
> module

why ? Do we really think that C/R implementations will be so different that
we will need C/R ops to support all of them ? I imagine that there could be
different models :

1. brute force : dump it all and kill
2. incremental
3. live migration
...

But I see all of them really tied to the kernel internals.

The first issues I see with this direction are some EXPORT_SYMBOL() that would
be useless without a 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.

OK that's integrated and Daniel's tools :

http://lxc.cvs.sourceforge.net/lxc/

one more reason to work on integration :)

C.

> 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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