[Beowulf] profiling memory bandwidth of a job

Lombard, David N david.n.lombard at intel.com
Fri Jan 9 14:15:48 EST 2004


From: Michael Arndt; Friday, January 09, 2004 1:55 AM
> 
> Hello,
> 
> Problem: to get the characteristics of a commercial numerical
>          CFD code on a Cluster with respect to memory bandwidth.
> 
> The Application is running single cpu jobs on SMP Nodes, no
> parallel application.
> 
> The runtimes show symptomes of concurring about memory bandwith.
> 
> I.e., if two One-CPU Jobs run on the dual CPU Node, the total run
> time is far more than twice the time of one job + e.g 30 % penalty for
> ressource competition of both jobs on a SMP Node.
> 
> Question: Is it possible, to show with standard linux profiling
commands
>           that really memory bandwidth is the issue ?
> 
> (Memory requirements and disk IO rate of the jobs are moderate, as far
>  as iostat / top shows)

I'm not sure about profiling tools, but running the job on systems with
differing memory configurations (and nothing else) can certainly
quantify the impact of memory bandwidth.

You also state that disk I/O is a potentially significant factor.  If it
is, which is a little odd for a CFD app, you also need to consider that.

Also look at memory size as an issue potentially affecting multiple
jobs.

-- 
David N. Lombard
 
My comments represent my opinions, not those of Intel Corporation.
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