Multilevel Queues Scheduling

Multilevel Queue Scheduling

Definition: Multilevel Queue Scheduling divides the ready queue into multiple separate queues, each with its own priority level and scheduling algorithm. A process is permanently assigned to one of these queues based on characteristics like memory size, type (interactive/batch), or priority.

Key Features:

• Queue Structure: Multiple distinct queues (e.g., Foreground, Background)

• Process Assignment: Permanent to one queue

• Scheduling Within Queue: Each queue can have a different scheduling algorithm (e.g., RR for Foreground, FCFS for Background)

• Scheduling Among Queues:

  • Fixed Priority Scheduling: Always schedule from highest priority queue first
  • Time Slicing Among Queues: CPU time split across queues (e.g., 80% to Foreground, 20% to Background)

• Drawback: Processes in lower-priority queues can suffer starvation

• Solution: Time slicing across queues or aging within queues