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

[Hanjun Kim]

Hi Pavan,

Thank you for your reply.
I am working on parallelization techniques with MPI, so various
programs (especially SPEC benchmarks) are my candidates. It will be
executed within one node for now, so it is OK to modify the MPICH2
code. I think it will be helpful for me to understand the system
buffer size effect on my technique. Which parts of the code should I
modify?

Thank you.

Best,
Hanjun

On Fri, Apr 23, 2010 at 6:51 PM, Pavan Balaji <balaji at mcs.anl.gov> wrote:
>
> 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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>
> --
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji
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