[GE users] wildly innacurate cpu usage, SGE 6.0u4

Lydia Heck lydia.heck at durham.ac.uk
Thu Jan 24 13:50:21 GMT 2008


Hi Aaron,

one of my colleagues, Henk Slim, has experienced the same problem and so we
started to investigate:

It turns out that on a parallel job, the wallclock time is calculated per
node which participates on that job, and is calculated from when all
the slot processes of that job for that node start and when all the slot
processes of the job on that node finish, irrespective of the number of slots
used on that node for that job.

The final wallclock time is then  sum_1,number_of_nodes  wallclock_node +
wallclock on master node.

If you then multiply the wallclock time reported by qacct with the number of
slots for the job you would get a totally wrong number for the resources.

Lydia


On Thu, 24 Jan 2008 aaron at cs.york.ac.uk wrote:

> Dear all,
>
> I was doing some detailed analysis of the job mix on our system from the
> past year to find out if the resources offered match those we provide so
> as to
> inform future purchasing decisions. At first it looked that our resources did
> not match from analyses run on the accounting file.
>
> On closer analysis, however, it seems that in a very few instances the cpu
> time used exceeded by order(s) of magnitude the ru_wallclock*slots time. Has
> anyone else seen this, and in what circumstances? The jobs affected seem
> to have failed.
>
> Regards, Aaron Turner
>
>
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------------------------------------------
Dr E L  Heck

University of Durham
Institute for Computational Cosmology
Ogden Centre
Department of Physics
South Road

DURHAM, DH1 3LE
United Kingdom

e-mail: lydia.heck at durham.ac.uk

Tel.: + 44 191 - 334 3628
Fax.: + 44 191 - 334 3645
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