Re: C/R without "leaks" (was: Re: Creating tasks on restart: userspace vs kernel)

Greg Kurz
2009-04-17T08:46:35Z

On Thu, 2009-04-16 at 20:12 +0400, Alexey Dobriyan wrote:
> On Thu, Apr 16, 2009 at 12:42:17AM +0200, Greg Kurz wrote:
> > On Wed, 2009-04-15 at 23:56 +0400, Alexey Dobriyan wrote:
>
> > > There are sockets and live netns as the most complex example. I'm not
> > > prepared to describe it exactly, but people wishing to do C/R with
> > > "leaks" should be very careful with their wishes.
> >
> > They should close their sockets before checkpoint and find/have some way
> > to reconnect after. This implies some kind of C/R awareness in the code
> > to be checkpointed.
>
> How do you imagine sshd closing sockets and reconnecting?

Dunno and it isn't really my concern... I'm interested in HPC jobs that
can collaborate with the C/R feature. For examples, those jobs that use
interconnect hardware that will never be *checkpointable*... Usually,
the batch manager tells the jobs it's going to be checkpointed, so that
it can disconnect/shrink memory/reach quiescent point, and reconnect
after resuming execution.

I understand you aim at supporting transparent C/R of connected TCP
sockets. Nice feature. Could you give use cases where it's *really*
helpful/needed/mandatory ?

--
Gregory Kurz gkurz@fr.ibm.com
Software Engineer @ IBM/Meiosys http://www.ibm.com
Tel +33 (0)534 638 479 Fax +33 (0)561 400 420

"Anarchy is about taking complete responsibility for yourself."
Alan Moore.