Fair Share and Priority

Slurm allows all groups to have equal opportunity to run calculations. If we consider the entire computing resource as a piece of pie, each group gets an equal piece of the pie. That group’s piece is then distributed equally to each user in the group. This concept is called “Fair Share”. The fair share is a multiplicative factor in computing a job’s “Priority”. At Pitt, we use a multi-factor priority system which includes:

  • Age – How long has the job been in the queue
  • Fair share – Has everyone had an equal opportunity to compute
  • Job size – Large core counts with short wall times are prioritized
  • Quality of service (QOS) – Shorter wall times are better
    • short (max: 24 hours) – QOS factor multiplied by 2
    • normal (max: 3 days) – QOS factor multiplied by 1
    • long (max: 6 days) – QOS factor multiplied by 0

To compute priority, one simply sums up all of the individual factors. Higher priorities will go into the queue first.