[Paraview] pvserver always shows 100% cpu usage

[Jacques Papper]

Just a quick note - I have noticed the same behavior with LAM-MPI, but not
with MPICH.
Jacques

2008/12/5 Paul Edwards <paul.m.edwards at gmail.com>

> Hi all,
>
> It just depends on how it is implemented with MPI.  There will be lower
> latency if it spins in a loop waiting for a message.  Here is a link to the
> FAQ which shows how you can stop this for OpenMPI:
>
> http://www.open-mpi.org/faq/?category=running#oversubscribing
> http://www.open-mpi.org/faq/?category=running#force-aggressive-degraded
>
> Regards,
> Paul
>
> 2008/12/5 John M. Patchett <patchett at lanl.gov>
>
> Hi Jens,
>>  If I recall correctly, your observation lies in the type of hardware you
>> are using.   I think some hardware allows a developer to leverage an
>> interrupt while some requires polling for a received message.   Design
>> requirements for MPI to be fast with low latency usually (I presume)
>> outweigh lowering heat production.
>>
>> I think I first noticed this issue with mvapich when infiniband was new.
>>  I don't think we had it with Myrinet 2000 or Gig-E.
>>
>> I also think ParaView is a normal mpi application, we just don't notice
>> machines spinning while waiting during batch processing, we just assume
>> they're working hard.
>>
>>
>> -John.
>>
>> On Dec 5, 2008, at 9:42 AM, Jens wrote:
>>
>>  Hi John,
>>>
>>> thanks for your answer. That makes sense. "Normal" mpi-apps are probably
>>> not written to wait for more things to do - they are simply always busy.
>>>
>>> It is just a pity that the cluster has to run 100% producing a lot of
>>> heat for nothing.
>>>
>>> So the MPI-lib will probably not change this behavior :( ? (I am using
>>> open-mpi 1.2.8)
>>>
>>> Greetings
>>> Jens
>>>
>>>
>>> John M. Patchett schrieb:
>>>
>>>> Hi Jens,
>>>>  Your pvserver is probably waiting on an MPI_Recv and your MPI
>>>> implementation is spinning.
>>>> You will note that process 0 probably isn't doing this, as the other
>>>> nodes are waiting on process 0 to send.
>>>> I have searched this problem all the way to the MPI developers as it's
>>>> easy to replicate without paraview and the MPI guys assure me the
>>>> alternatives are worse.
>>>> -John.
>>>>
>>>> On Dec 5, 2008, at 8:42 AM, Jens wrote:
>>>>
>>>>  Hi,
>>>>>
>>>>> if I run "mpirun -np 4 ./pvserver" on our cluster-node and connect from
>>>>> my client, this pvserver always shows 100% cpu usage - even if I do
>>>>> nothing at the client.
>>>>>
>>>>> Seems to me as if there is a loop waiting for the client to ask for
>>>>> action - but this loop is calling no wait/sleep function.
>>>>>
>>>>> Greetings
>>>>> Jens
>>>>> _______________________________________________
>>>>> ParaView mailing list
>>>>> ParaView at paraview.org
>>>>> http://www.paraview.org/mailman/listinfo/paraview
>>>>>
>>>>
>>>>
>> _______________________________________________
>> ParaView mailing list
>> ParaView at paraview.org
>> http://www.paraview.org/mailman/listinfo/paraview
>>
>
>
> _______________________________________________
> ParaView mailing list
> ParaView at paraview.org
> http://www.paraview.org/mailman/listinfo/paraview
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.paraview.org/pipermail/paraview/attachments/20081205/6b1760ab/attachment.htm>