Hello everybody,

I'm running maui and torque using fair share weight to balance user
activities. In principle that works fine. As I like to have the fair
share act on a longer time scale (several days), I also had a quite low
soft limit of 2 in order to guarantee that every user gets at least some
cpu time independent of the long term fair share. The idea was, of
course, that maui then fills up to the hard limits using the priorities
based on fair share.

However, what I had to learn is that the jobs - after the soft limits
are reached and before the hard limits are reached - are selected by the
backfill rules. And that leads to a situation, which doesn't seem very
logical: after a user a two jobs running and still a remaining job with
highest priority, maui places a reservation for this job and then fills
the rest up with shortest jobs first. Ok, then I thought, that we don't
need reservations and I switched that off, but only with the effect that
maui didn't do a reservation. It still wants to run that job next and
tries to find jobs fitting in as backfill starting with the smallest
walltime.

That is not very logical, because it regularly leads to the following
situation: Assume 70 free cpus, 70 jobs from user A and B, user A with
high priority, user B with short jobs. Due to soft limits A and B get
two slots, after that (hard limit of 70 jobs) all remaining slots are
assigned to B although A has higher priority. The high priority job of A
hinders A to get more than cpu than the soft limit tells.

At the moment this is somehow solved by having no soft limits and
a fair share with much shorter intervals. Also the number of idle jobs
is restricted and thus the accumulation of queuing time based priority
is limited not to give advantage to users submitting hundreds of jobs.
However, I'm curious whether there is some way to have the available
slots between soft and hard limits distributed according to priorities
only.

Thanks in advance and best regards,    
Volker

-- 
Dr. Volker Hejny
Institut für Kernphysik
Phone: +49 2461 61 6853
Fax: +49 2461 61 3930

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