CODEWITHSUNDEEP
matlabparallel-processingdistributed-computing
nahsivar
nahsivar

Reputation: 1099

What is the Overhead of matlabpool?

Could anyone point to me what is the overhead of running a matlabpool ?

I started a matlabpool :

matlabpool open 132procs 100
Starting matlabpool using the '132procs' configuration ... connected to 100 labs.

And followed cpu usage on the nodes as :

pdsh -A ps aux |grep dmlworker

When I launch the matlabpool, it starts with ~35% cpu usage on average and when the pool is not being used it slowly (in 5-7 minutes) goes down to ~2% on average.

Is this normal ? What is the typical overhead ? Does that change if matlabpooljob is launched as a "batch" job ?

Upvotes: 3

Views: 284

Answers (1)

James Beilby
James Beilby

Reputation: 1471

This is normal. ps aux reports the average CPU utilization since the process was started, not over a rolling window. This means that, although the workers initialize relatively quickly and then become idle, it will take longer for this to reflect in CPU%. This is different to the Linux top command, for example, which will reflect the utilization since the last screen update in %CPU.

As for typical overhead, this depends on a number of factors: clearly the number of workers, the rate and data size of jobs submitted (as well as in maintaining the worker processes, there is some overhead in marshalling input and output, which is not part of "useful computation"), whether the Matlab pool is local or attached to a job manager, and the Matlab version and O/S.

From experience, as a rough guide on a modern *nix server, I would think an idle worker should be not be consuming more than 20% of a single core (e.g. <~1% total CPU utilization on a 16-core box) after initilization, unless there is a configuration issue. I should not expect this to be influenced by what kind of jobs you are submitting (whether using "createJob" or "batch" or "parfor" for example): the workers and communication mechanisms underneath are essentially the same.

Upvotes: 1

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