The job scheduler and the queue

• How does the queue work?

• Let's look graphically at jobs presently running.

• x-axis: cores, one thread per core

• y-axis: time

• We see some holes where we may fit jobs already!

• Let's see which type of jobs that can fit!

• 4 one-core jobs can run immediately (or a 4-core wide job).*

  • The jobs are too long to fit at core number 9-13.

• A 5-core job has to wait.*

  • Too long to fit in cores 9-13 and too wide to fit in the last cores.

• Easiest to schedule single-threaded, short jobs

Tip

• You don't see the queue graphically, however.
• But, overall:
  • short and narrow jobs will start fast
  • test and development jobs can get use of specific development nodes if they are shorter than 1 hour and uses up to two nodes.
  • waste of resources unless you have a parallel program or need all the memory, e.g. 128 GB per node