Friday 9 March 2012

Multilevel Queue


  • Ready queue is partitioned into separate queues:
  • foreground (interactive)
  • background (batch)
  • Each queue has its own scheduling algorithm, 
  • foreground – RR
  • background – FCFS
  • Scheduling must be done between the queues.
  1. Fixed priority scheduling; (i.e., serve all from foreground then from background).  Possibility of starvation.
  2. Time slice – each queue gets a certain amount of CPU time which it can schedule amongst its processes; i.e., 80% to foreground in RR
  3. 20% to background in FCFS 

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