[Paraview] pvserver always shows 100% cpu usage

[John M. Patchett]

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
>>