[Devel] Re: [RFC v13][PATCH 00/14] Kernel based checkpoint/restart

[Dave Hansen]

On Thu, 2009-02-12 at 17:05 -0600, Matt Mackall wrote:
> On Thu, 2009-02-12 at 14:57 -0800, Dave Hansen wrote:
> > > Also, what happens if I checkpoint a process in 2.6.30 and restore it in
> > > 2.6.31 which has an expanded idea of what should be restored? Do your
> > > file formats handle this sort of forward compatibility or am I
> > > restricted to one kernel?
> > 
> > In general, you're restricted to one kernel.  But, people have mentioned
> > that, if the formats change, we should be able to write in-userspace
> > converters for the checkpoint files.  
> 
> I mentioned this because it seems like a key use case is upgrading
> kernels out from under long-lived applications.

The key users as I envision it aren't really kernel hackers who are
always running 2.6-next and running radically different kernels from
moment to moment. :)

Distros are pretty picky about changing things internal to the kernel
during errata updates or even service packs.  While that can be a pain
for some of us developers trying to get features and fixes in, it is a
godsend for trying to do something like process migration across an
update.

My random speculation would be that for things that if a kernel upgrade
can be performed with ksplice (http://www.ksplice.com/) -- the original
non-fancy version at least -- we can probably migrate across the
upgrade.

-- Dave

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