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Subject: [OMPI users] Profiling performance by forcing transport choice.
From: Nifty Tom Mitchell (niftyompi_at_[hidden])
Date: 2009-07-20 16:03:04


On Thu, Jun 25, 2009 at 08:37:21PM -0400, Jeff Squyres wrote:
> Subject: Re: [OMPI users] 50%performance reduction due to OpenMPI v 1.3.2forcing
> allMPI traffic over Ethernet instead of using Infiniband

<musing>

While the previous thread on "performance reduction" went left, right,
forward and beyond the initial topic it tickled an idea for application
profiling or characterizing.

What if the various transports (btl) had knobs that permitted stepwise
insertion of bandwidth limits and latency limits etc. so the application
might be characterized better?

Most micro benchmarks are designed to measure various hardware characteristics
but it is moderately hard to know what an application depends on.

The value of this is that:
        *the application authors might learn something
        about their code that is hard to know at a well
        abstracted API level.

        *the purchasing decision maker would have the ability
        to access a well instrumented cluster and build a
        weighted value equation to help structure the decision.

        *the hardware vendor can learn what is valuable when deciding
        what feature and function needs the most attention/ transistors.

i.e. it might be as valuable to benchmark "your code" on a single well
instrumented platform as it might be to benchmark all the hardware you
can get "yer hands on".

</musing>

-- 
	T o m  M i t c h e l l 
	Found me a new hat, now what?