[OS]Basic Scheduling algorithms

FCFS(First-Come-First-Service)

• Non-preemptive scheduling
• Scheduling criteria
  • ready queue
• High resource utilization
  • Low scheduling overhead
• Good for Batch system, Not good for interactive system
• Weakness
  • Convoy effect
  • long response time

RR(Round-Robin)

• Preemptive scheduling
• Scheduling criteria
  • ready queue
• Time quantum
  • System parameter
  • Timer-runout
  • Anti-monopoly
  • High context switch overhead
• Good for interactive system

SPN (Shortest-Process-Next)

• Non-preemptive scheduling
• Scheduling criteria
  • burst time
    • SJF(Shortest Job First) scheduling

SRTN(Shortest Remaining Time Next)

• Preemptive scheduling
• Context switching overhead

HRRN(High-REsponse-Ratio-Next)

• SPN + Aging concepts, Non-preemptive scheduling
• Aging concepts
• Scheduing criteria
  • Response ratio = (WT + BT) / BT

MLQ(Multi-level Queue)

• Have a ready queue for each Job (or Priority)
  • Can’t get out of assigned queue
• Weakness
  • overhead
  • Low priority queue starvation

MFQ(Multi-level Feedback Queue)

• Allow process to move between Queue
• Dynamic priority
• Preemptive scheduling
• Favor short burst-time processes
• Favor I/O bounded processes
• Improve adaptability

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Reference

Process Scheduling