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Subject: Re: [OMPI users] EXTERNAL: Re: Need advice on performance problem
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-06-11 20:30:11


Great! Would you mind showing the revised table? I'm curious as to the relative performance.

On Jun 11, 2013, at 4:53 PM, eblosch_at_[hidden] wrote:

> Problem solved. I did not configure with --with-mxm=/opt/mellanox/mcm and
> this location was not auto-detected. Once I rebuilt with this option,
> everything worked fine. Scaled better than MVAPICH out to 800. MVAPICH
> configure log showed that it had found this component of the OFED stack.
>
> Ed
>
>
>> If you run at 224 and things look okay, then I would suspect something in
>> the upper level switch that spans cabinets. At that point, I'd have to
>> leave it to Mellanox to advise.
>>
>>
>> On Jun 11, 2013, at 6:55 AM, "Blosch, Edwin L" <edwin.l.blosch_at_[hidden]>
>> wrote:
>>
>>> I tried adding "-mca btl openib,sm,self" but it did not make any
>>> difference.
>>>
>>> Jesus’ e-mail this morning has got me thinking. In our system, each
>>> cabinet has 224 cores, and we are reaching a different level of the
>>> system architecture when we go beyond 224. I got an additional data
>>> point at 256 and found that performance is already falling off. Perhaps
>>> I did not build OpenMPI properly to support the Mellanox adapters that
>>> are used in the backplane, or I need some configuration setting similar
>>> to FAQ #19 in the Tuning/Openfabrics section.
>>>
>>> From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On
>>> Behalf Of Ralph Castain
>>> Sent: Sunday, June 09, 2013 6:48 PM
>>> To: Open MPI Users
>>> Subject: Re: [OMPI users] EXTERNAL: Re: Need advice on performance
>>> problem
>>>
>>> Strange - it looks like a classic oversubscription behavior. Another
>>> possibility is that it isn't using IB for some reason when extended to
>>> the other nodes. What does your cmd line look like? Have you tried
>>> adding "-mca btl openib,sm,self" just to ensure it doesn't use TCP for
>>> some reason?
>>>
>>>
>>> On Jun 9, 2013, at 4:31 PM, "Blosch, Edwin L" <edwin.l.blosch_at_[hidden]>
>>> wrote:
>>>
>>>
>>> Correct. 20 nodes, 8 cores per dual-socket on each node = 360.
>>>
>>> From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On
>>> Behalf Of Ralph Castain
>>> Sent: Sunday, June 09, 2013 6:18 PM
>>> To: Open MPI Users
>>> Subject: Re: [OMPI users] EXTERNAL: Re: Need advice on performance
>>> problem
>>>
>>> So, just to be sure - when you run 320 "cores", you are running across
>>> 20 nodes?
>>>
>>> Just want to ensure we are using "core" the same way - some people
>>> confuse cores with hyperthreads.
>>>
>>> On Jun 9, 2013, at 3:50 PM, "Blosch, Edwin L" <edwin.l.blosch_at_[hidden]>
>>> wrote:
>>>
>>>
>>>
>>> 16. dual-socket Xeon, E5-2670.
>>>
>>> I am trying a larger model to see if the performance drop-off happens at
>>> a different number of cores.
>>> Also I’m running some intermediate core-count sizes to refine the curve
>>> a bit.
>>> I also added mpi_show_mca_params all, and at the same time,
>>> btl_openib_use_eager_rdma 1, just to see if that does anything.
>>>
>>> From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On
>>> Behalf Of Ralph Castain
>>> Sent: Sunday, June 09, 2013 5:04 PM
>>> To: Open MPI Users
>>> Subject: EXTERNAL: Re: [OMPI users] Need advice on performance problem
>>>
>>> Looks to me like things are okay thru 160, and then things fall apart
>>> after that point. How many cores are on a node?
>>>
>>>
>>> On Jun 9, 2013, at 1:59 PM, "Blosch, Edwin L" <edwin.l.blosch_at_[hidden]>
>>> wrote:
>>>
>>>
>>>
>>>
>>> I’m having some trouble getting good scaling with OpenMPI 1.6.4 and I
>>> don’t know where to start looking. This is an Infiniband FDR network
>>> with Sandy Bridge nodes. I am using affinity (--bind-to-core) but no
>>> other options. As the number of cores goes up, the message sizes are
>>> typically going down. There seem to be lots of options in the FAQ, and I
>>> would welcome any advice on where to start. All these timings are on a
>>> completely empty system except for me.
>>>
>>> Thanks
>>>
>>>
>>> MPI # cores Ave. Rate Std. Dev. % # timings
>>> Speedup Efficiency
>>> ================================================================================================
>>> MVAPICH | 16 | 8.6783 | 0.995 % | 2 |
>>> 16.000 | 1.0000
>>> MVAPICH | 48 | 8.7665 | 1.937 % | 3 |
>>> 47.517 | 0.9899
>>> MVAPICH | 80 | 8.8900 | 2.291 % | 3 |
>>> 78.095 | 0.9762
>>> MVAPICH | 160 | 8.9897 | 2.409 % | 3 |
>>> 154.457 | 0.9654
>>> MVAPICH | 320 | 8.9780 | 2.801 % | 3 |
>>> 309.317 | 0.9666
>>> MVAPICH | 480 | 8.9704 | 2.316 % | 3 |
>>> 464.366 | 0.9674
>>> MVAPICH | 640 | 9.0792 | 1.138 % | 3 |
>>> 611.739 | 0.9558
>>> MVAPICH | 720 | 9.1328 | 1.052 % | 3 |
>>> 684.162 | 0.9502
>>> MVAPICH | 800 | 9.1945 | 0.773 % | 3 |
>>> 755.079 | 0.9438
>>> OpenMPI | 16 | 8.6743 | 2.335 % | 2 |
>>> 16.000 | 1.0000
>>> OpenMPI | 48 | 8.7826 | 1.605 % | 2 |
>>> 47.408 | 0.9877
>>> OpenMPI | 80 | 8.8861 | 0.120 % | 2 |
>>> 78.093 | 0.9762
>>> OpenMPI | 160 | 8.9774 | 0.785 % | 2 |
>>> 154.598 | 0.9662
>>> OpenMPI | 320 | 12.0585 | 16.950 % | 2 |
>>> 230.191 | 0.7193
>>> OpenMPI | 480 | 14.8330 | 1.300 % | 2 |
>>> 280.701 | 0.5848
>>> OpenMPI | 640 | 17.1723 | 2.577 % | 3 |
>>> 323.283 | 0.5051
>>> OpenMPI | 720 | 18.2153 | 2.798 % | 3 |
>>> 342.868 | 0.4762
>>> OpenMPI | 800 | 19.3603 | 2.254 % | 3 |
>>> 358.434 | 0.4480
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