[Beowulf] Lowered latency with multi-rail IB?

Håkon Bugge hbugge at platform.com
Fri Mar 27 13:37:28 EDT 2009

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.

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