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

Louis Rilling
2008-09-03T14:06:50Z

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On Wed, Sep 03, 2008 at 03:49:51PM +0200, Louis Rilling wrote:
> On Wed, Sep 03, 2008 at 02:57:47PM +0400, 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
> >
> >
> > 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.
>
> Thank you Andrey for having highlighted the differences with Oren's approach,
> and for having split this patchset. Few remarks in reply to the patches.

Forgot a global comment: you will probably get the same (rather pointless for a
proof of concept, IMHO) requests as Oren got, to
1) improve coding style:
a) especially avoid error handling like:
err = foo();
if (!err)
err = bar();
if (!err)
err = baz();

and prefer
err = foo();
if (err)
goto foo_err;
err = bar();
...

b) do not write conditions on a single line, like
if (foo) bar;

2) put arch-dependent code in arch/ subdirs.
3) I probably forgot other ones.

I obviously do not personally request you to take these requests into account ;)

Louis

--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes

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