[Beowulf] MPI performance gain with jumbo frames

Jeffrey B. Layton laytonjb at charter.net
Mon Jun 11 11:57:09 EDT 2007


Doug brings up some good points. If you want to try Jumbo
Frames to improve MPI performance you might have to
tweak the TCP buffers as well. There are some links around
the web on this. Sometimes it helps performance, sometimes
it doesn't. Your mileage may vary.

Jeff

> 1) The results you reference are rather old. Does this
>    reflect your hardware?
>
> 2) To support Jumbo Frames you need both NICs and a switch
>    that support them.
>
> 3) It is possible to achieve wire speed from
>    GigE, you need something other then 32 bit PCI
>    connections, however. (PCIe, PCI-X)
>
> 4) While Jumbo Frames can help NFS, the effect on MPI
>    can vary by application. Have you run any tests to
>    see exactly what your network performance is?
>    (i.e. Netpipe)
>
> You may find these articles helpful:
>
> http://www.clustermonkey.net//content/view/38/34/
>
> http://www.clustermonkey.net//content/view/39/34/
>
> --
> Doug
>
>
>   
>> hi all,
>>
>> new to this list, so don't know if this is offtopic.
>>
>> i'd like to know experiences about MPI performance gain with jumbo frames.
>> i
>> manage a beowulf cluster (42 athlon xp, gentoo linux) with gigabit
>> ethernet
>> where fluent, openfoam and other mpi apps are run.
>>
>> with NFS i'm sure wich kind of gain i would have, but with MPI apps i'm
>> worried about after seeing this page
>> http://www.scl.ameslab.gov/Projects/IBMCluster/Benchmarks.html
>>
>> regards
>>
>>
>>
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>> 
>>
>>     
>
>
> --
> Doug
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>
>   

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