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Subject: Re: [OMPI users] EXTERNAL: Re: Need advice on performance problem
From: eblosch_at_[hidden]
Date: 2013-06-11 19:53:40


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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