[Beowulf] Slection from processor choices; Requesting Giudence

Ron Brightwell rbbrigh at sandia.gov
Fri Jun 16 17:55:35 EDT 2006


> 
> > - The network/MPI combination is fairly critical to good performance and 
> > to
> > price/performance. I have done some benchmarks where the right MPI library
> > on GigE produces faster results than a bad MPI library on Myrinet. Seems
> > counter-intuitive, but I've seen it.
> > Jeff
> 
> Jeff, we know how some people can mess up installs, but if you have gigabit 
> ethernet,
> with a one way pingpong latency of like 50-100 us if you're lucky, which is 
> not using DMA i
> guess by default; in short nonstop interrupting your cpu,
> versus newer myri cards that are probably under 3 us, factor 20 to 30 
> advantage to
> myri then you need to really not manage to install the network to let 
> gigabit ethernet work better.
> 
> That said it's not easy of course to install the network, but let's not 
> assume that someone who
> builds a cluster doesn't manage to install the hardware he gets.
> 
> For that huge amount of money from the highend manufacturers that you pay 
> for their hardware, you
> DO get great support if you really don't manage to install it.
> 
> There is not really exceptions to that.

I think I missed something...

At what step in the installation process do you make sure that the performance
of your application is tied directly to ping-pong latency?

-Ron


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