[Beowulf] Lowered latency with multi-rail IB?

[Håkon Bugge]

On Mar 27, 2009, at 18:20 , Craig Tierney wrote:

> What about using multi-rail to increase message rate?  That isn't
> the same as latency, but if you put messages on both wires you
> should get more.

Exactly why we saw almost 2x speedup on message rate (latency)  
sensitive apps using Platform MPI. We call the technique alternating;  
any communicating peer will use a HCA or port, but a single MPI  
process will alternate between different HCAs (or ports), depending on  
which peer he communicates with.


Håkon