[Beowulf] Home beowulf - NIC latencies

[Josip Loncaric]

Rossen Dimitrov wrote:
> 
> So, if you really want to optimize the use of your cluster resources, in 
> addition to the network and compute nodes, you will need to also 
> consider the communication middleware and the design of your application 
> and how they all work together.

Are there any projects that would expand the ability of MPI application 
programmers to provide performance hints to the MPI library?  For 
example, hints indicating that certain messages are latency sensitive 
whereas others need optimal bandwidth and low CPU overhead?

One can already obtain some MPI performance data through the PMPI 
mechanism, and Rossen is helping develop MPI PERUSE 
(http://www.mpi-peruse.org/) intended to provide even more detail.  I'm 
asking about the other direction of information flow, i.e. performance 
hints from the application to the MPI layer...

Ideally, such hints would be propagated fairly close to the actual 
hardware, e.g. application hints would guide the MPI library in 
selecting improved interrupt mitigation strategies used by the network 
interfaces (assuming that a suitable API exists for the underlaying 
hardware).

Sincerely,
Josip