SLURM/Priority

SLURM at UMIACS is configured to prioritize jobs based on a number of factors, termed multifactor priority in SLURM.

These factors include:

• Age of job i.e. time spent waiting to run in the queue
• Partition job was submitted to
• Fair-share of resources
• "Nice" value that job was submitted with

Age

The longer a job is eligible to run but cannot due to all available resources being taken up increases the job's priority to be scheduled as time goes on. The priority modifier for this factor reaches its limit after 7 days.

Partition

The partition named scavenger on each of our clusters always has a lower priority factor for its jobs than all other partitions on that cluster. As mentioned in other UMIACS cluster-specific documentation, jobs submitted to this partition are also preemptable. These two design choices give the partition its name; jobs submitted to the scavenger partition "scavenge" for available resources on the cluster rather than consume a dedicated chunk of resources and are interrupted by jobs seeking to consume dedicated chunks.

All other partitions on our clusters have the same priority factor.

Nice value

This is a submission argument that you as the user can include in your jobs to deprioritize them relative to one another. Larger values will deprioritize jobs e.g.,

srun --pty --qos=default --mem 1gb --time=01:00:00 --nice=2 bash

will have lower priority than

srun --pty --qos=default --mem 1gb --time=01:00:00 --nice=1 bash

which will have lower priority than

srun --pty --qos=default --mem 1gb --time=01:00:00 bash

assuming all three jobs were submitted at the same time. You cannot use negative values for this argument.