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Subject: Re: [OMPI users] memory limits on remote nodes
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-10-07 18:43:07


On Oct 6, 2010, at 11:25 PM, David Turner wrote:

> Hi Ralph,
>
>> 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?
>
> 1.4.2, with 1.4.1 available, and 1.4.3 waiting in the wings.
> I would love to test any patch you could come up with.
> The ability to set any valid limit to any valid value,
> applied equally to all processes, would go a long way in
> making our environment more stable. Thanks!

Just to be sure I'm on track here: setting the soft limit will cause the job to terminate if any process attempts to use more memory than that limit. This is what you want to have happen?

I ask because we have a memory usage monitor in OMPI right now (in the trunk, not in 1.4 series) that does exactly what I've described, and the limit can be set for each job. So I'm wondering if the answer here is just to suggest you try with the trunk and see if it does what you want?

>
>>> 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
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Best regards,
>
> David Turner
> User Services Group email: dpturner_at_[hidden]
> NERSC Division phone: (510) 486-4027
> Lawrence Berkeley Lab fax: (510) 486-4316
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users