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From: George Bosilca (bosilca_at_[hidden])
Date: 2007-06-06 17:37:53


If you use one of the latest version of MX (such as 1.2.0f) there
will be less than 0.15 micro-second difference between the MTL and
BTL MX. This version of MX allow us to do the matching outside the
NIC, which decrease the overhead for small messages. In terms of
bandwidth the BTL MX is somehow faster (40Mbs more than the MTL) on a
2Gbs network.

   Thanks,
     george.

On Jun 6, 2007, at 5:23 PM, Tim Prins wrote:

> Note that since you are setting OMPI_MCA_pml to cm, OMPI_MCA_btl
> will have no
> effect. You may try setting OMPI_MCA_pml=ob1, and trying your
> measurements
> again, but we generally get better performance with the cm pml than
> then ob1
> pml.
>
> Tim
>
> On Wednesday 06 June 2007 12:54:26 pm George Bosilca wrote:
>> Which one is the latency with Open MPI ? Which version of Open MPI ?
>>
>> You might want to use OMPI_MCA_btl=mx,self to see if it makes any
>> difference.
>>
>> Thanks,
>> george.
>>
>> On Jun 6, 2007, at 12:26 PM, Maestas, Christopher Daniel wrote:
>>> With 2 nodes using 1.1.7 with the patch we measured (using mpich-mx
>>> 1.2.7..4):
>>> 3.07us
>>>
>>> With mx 1.2.1-rc18 we measure:
>>> 3.69 us
>>> And with mpich-mx 1.2.7..4 we see:
>>> 3.20us
>>>
>>> Our Open MPI settings:
>>> ---
>>> # env | grep OMPI
>>> OMPI_MCA_pml=cm
>>> OMPI_MCA_mpi_keep_hostnames=1
>>> OMPI_MCA_oob_tcp_include=eth0
>>> OMPI_MCA_btl=mx,sm,self
>>>
>>> Does anyone know why the latency would be slightly higher using
>>> Open MPI
>>> versus MPICH-MX?
>>>
>>> Thanks,
>>> -cdm
>>>
>>>
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>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
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