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Subject: Re: [OMPI users] memory limits on remote nodes
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-10-06 20:31:32

There is an MCA param that tells the orted to set its usage limits to the hard limit:

                MCA opal: parameter "opal_set_max_sys_limits" (current value: <0>, data source: default value)
                          Set to non-zero to automatically set any system-imposed limits to the maximum allowed

The orted could be used to set the soft limit down from that value on a per-job basis, but we didn't provide a mechanism for specifying it. Would be relatively easy to do, though.

What version are you using? If I create a patch, would you be willing to test it?

On Oct 6, 2010, at 5:55 PM, David Turner wrote:

> Hi,
> We would like to set process memory limits (vmemoryuse, in csh
> terms) on remote processes. Our batch system is torque/moab.
> The nodes of our cluster each have 24GB of physical memory, of
> which 4GB is taken up by the kernel and the root file system.
> Note that these are diskless nodes, so no swap either.
> We can globally set the per-process limit to 2.5GB. This works
> fine if applications run "packed": 8 MPI tasks running on each
> 8-core node, for an aggregate limit of 20GB. However, if a job
> only wants to run 4 tasks, the soft limit can safely be raised
> to 5GB. 2 tasks, 10GB. 1 task, the full 20GB.
> Upping the soft limit in the batch script itself only affects
> the "head node" of the job. Since limits are not part of the
> "environment", I can find no way propagate them to remote nodes.
> If I understand how this all works, the remote processes are
> started by orted, and therefore inherit its limits. Is there
> any sort of orted configuration that can help here? Any other
> thoughts about how to approach this?
> Thanks!
> --
> Best regards,
> David Turner
> User Services Group email: dpturner_at_[hidden]
> NERSC Division phone: (510) 486-4027
> Lawrence Berkeley Lab fax: (510) 486-4316
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