[mpich-discuss] Latency or the B/W, which is the bottleneck for most MPI codes?

[Micha Feigin]

Depends,

Short messages will be more affected by latency, long messages will be more affected by B/W.

On Fri, 5 Mar 2010 14:55:32 -0600
junli gu <junligu at illinois.edu> wrote:

> Hi everyone:
> 
>   I am wondering to most MPI codes, which is the performance bottleneck, the
> latency or the B/W?
> 
>   I am doing research to optimize the cache-coherent shared memory
> architecture to run MPI codes more efficiently. Although I am trying to
> reduce the latency for message data transferring, then I realized that maybe
> the B/W is the real bottleneck. I have heard the comments that most
> well-written MPI codes  are not latency-sensitive but B/W sensitive. So
> instead of making single message transfer faster, increasing the B/W to
> transfer the chunk of data faster is the right way to improve performance.
> 
>   Can you give us some comments about this?
> 
>   Thank you in advance!
>