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Subject: Re: [OMPI users] Questions on /tmp/openmpi-sessions-userid directory
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-03-07 11:21:53

On Mar 7, 2010, at 2:55 AM, Gijsbert Wiesenekker wrote:

> I was having non-reproducible hangs in an OpenMPI program. While troubleshooting this problem I found that there were many temporary directories in my /tmp/openmpi-sessions-userid directory (probably the result of MPI_Abort aborted OpenMPI programs). I cleaned those directories up and it looks like the hangs have gone.
> My questions are:
> It looks like the name of the temporary directory in /tmp/openmpi-sessions-userid directory is a process-id. What happens when an OpenMPI program starts and the temporary directory in /tmp/openmpi-sessions-userid already exists?

It'll just overwrite what is already there. I confess that the code has not been tested for that situation, though, so I can't guarantee that response.

> Could existing temporary directories in /tmp/openmpi-sessions-userid cause an OpenMPI program to hang?

Given your observations, I guess the answer has to be "yes", though I wouldn't have expected it. The typical behavior in this scenario is for the application to error out during MPI_Init when it finds that there isn't enough space in /tmp for the session directory - and that is caused not by the directory itself, but rather by the shared memory backing file that resides in the session dir tree and can be quite large.

> Is there a way to ensure that the temporary directory created in /tmp/openmpi-sessions-userid is always removed after an OpenMPI program has run?

It really, really helps to know what version you are using. We just found a bug in the 1.3/1.4 series that was causing the apps not to cleanup in exactly this scenario - that is fixed in the upcoming 1.4.2 release. The older 1.2 series had this problem as well, but we aren't going back to fix it. :-)

> Regards,
> Gijsbert
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