I'm quite sure that the CM CPC stuff (both IBCM -- which doesn't fully
work anyway -- and RDMA CM) will timeout and Bad Things will happen if
you interrupt it in the middle of some network transactions. The
(kernel-imposed) timeout for RDMACM is pretty short -- on the order of
a minute or two.
On Dec 11, 2008, at 3:19 PM, Josh Hursey wrote:
I would expect that you will hit problems with timeouts throughout
the codebase as Jeff mentioned, particularly with network
connections. Having a 'prepare to suspend' signal followed by a
'suspend now' signal might work since it should provide enough of a
window to ready the application for the suspension.
I think the first step is to try it, being sure to let the process
stay suspended for a considerable amount of time (15 min to an hour
at least) and see what effects this has. I would expect a series of
errors, but I haven't tried it so I can't say for sure.
If there are errors then looking at the internal notification stuff
that the C/R mechanism uses would be a good place to start since it
handles these types of issues for a checkpoint operation.
-- Josh
On Dec 11, 2008, at 3:08 PM, Jeff Squyres wrote:
On Dec 11, 2008, at 2:55 PM, Terry Dontje wrote:
Well under SGE it allows you to have SGE send mpirun SIGUSR1 so
many minutes before sending the Suspend signal.
My point is that the right approach might be to work in the context
of Josh's CR stuff -- he's already got hooks for "do this right
before pausing for checkpoint" / "do this right after resuming", etc.
Sure, we're not checkpointing, but several of the characteristics
of this action are pretty similar to what is required for
checkpointing/restarting. So it might be good to use that
framework for it...?
--
Jeff Squyres
Cisco Systems
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