[torqueusers] walltime

[andrealphus]

Does walltime matter in terms of optimizing the scheduler? E.g. if I
have a job that will only run for 10 minutes, but I set the walltime
to 999 hours, will it have any detrimental effect (assuming it
executes cleanly)?

Thanks!

[Troy Baer]

Post by andrealphus
Does walltime matter in terms of optimizing the scheduler? E.g. if I
have a job that will only run for 10 minutes, but I set the walltime
to 999 hours, will it have any detrimental effect (assuming it
executes cleanly)?

It depends on what scheduler you're using, but certainly any scheduler
that uses advance reservations (e.g. Maui, Moab, and several others)
will do a better jobs when jobs' walltime requests are as accurate as
possible.

--Troy

[David Beer]

It depends on your scheduler, but Moab (and I believe Maui) perform future
scheduling, where they attempt to decide what will run after the current
jobs finish. These predictions will be off if the walltime is drastically
different from the actual runtime. Another feature that would be affected
is backfilling. If a large job has priority but won't start for 20 minutes,
Moab will look for short jobs to fill the empty spots for the next 20
minutes. If a job only takes 10, but says it'll take 999 hours, it wouldn't
run during that time, but if the walltime were correct, it would be able to
start that job during the backfill period.

Post by andrealphus
Does walltime matter in terms of optimizing the scheduler? E.g. if I
have a job that will only run for 10 minutes, but I set the walltime
to 999 hours, will it have any detrimental effect (assuming it
executes cleanly)?
Thanks!
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