[mpich-discuss] How to change system buffer size for MPI_Send and MPI_Recv?

[Pavan Balaji]

Is all communication within the same node? There's no easy way to 
increase this size without modifying the MPICH2 code. Also, that's not 
really a good solution, since it might break on some other network.

What exactly is your application trying to do? It sounds like it might 
be better for you to prepost the receive (MPI_Irecv) and enable 
asynchronous progress for data to be sent out on demand. In 
MPICH2-1.2.1p1, there's an experimental version available, if you'd like 
to use it (configure option --enable-async-process). In the MPICH2 1.3.x 
series, it is being compiled in by default, and is switched on/off using 
an environment variable.

  -- Pavan

On 04/23/2010 04:46 PM, Hanjun Kim wrote:
> Hi,
> 
> I installed mpich2 on a 24-core SMP machine(64bit ubuntu), and
> parallelized several programs with MPI. In general, the programs
> performed well. However, when large amount of data were sent through
> MPI_Send and Recv, the sender became blocked until the receiver
> received the data, and its performance became degraded. Is there some
> preset system buffer size for MPI_Send and MPI_Recv? If so, how can I
> increase the system buffer size? I believe if the system buffer size
> of MPI_Send is increased, it will be helpful to get better
> performance.
> 
> Thank you in advance.
> 
> Best,
> Hanjun
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> mpich-discuss at mcs.anl.gov
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-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji