Preemptive and Non-Preemptive Schedulers

Preemptive Scheduling

• The operating system can interrupt a process and switch to another process.
• The scheduler can preempt a process at any time.
• Advantages:
  • Improved responsiveness.
  • Better support for interactive processes.
• Disadvantages:
  • Increased overhead due to context switching.
  • Potential for starvation if not implemented correctly.

Non-Preemptive Scheduling

• A process runs until it completes or is blocked.
• The scheduler cannot interrupt a process.
• Advantages:
  • Less overhead due to context switching.
  • Simpler implementation.
• Disadvantages:
  • Poor responsiveness.
  • Potential for long processes to monopolize the CPU.

Comparison

Criteria	Preemptive	Non-Preemptive
Interruptibility	Yes	No
Responsiveness	Better	Poor
Overhead	Higher	Lower
Complexity	More complex	Simpler