Introduction

Table of contents

In an operating system, the scheduler is responsible for determining which process gets access to the CPU and when. There are two types of scheduling algorithms used by operating systems: preemptive and non-preemptive scheduling.

Preemptive Scheduling

In preemptive scheduling, a process can be interrupted by a higher-priority process at any time. The scheduler decides which process should be given access to the CPU based on the process’s priority level. If a higher-priority process becomes available, the currently running process is preempted, and the higher-priority process is given access to the CPU.

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Advantages of Preemptive Scheduling

  • Higher-priority processes can be given immediate access to the CPU, increasing system responsiveness.
  • Can prevent low-priority processes from hogging the CPU for an extended period.

Disadvantages of Preemptive Scheduling

  • Overhead from frequent context switching can impact system performance.
  • Can cause some processes to be starved of CPU time if higher-priority processes are continuously being added to the system.

Non-Preemptive Scheduling

In non-preemptive scheduling, a process continues to run until it voluntarily relinquishes the CPU or is blocked by an I/O request. The scheduler decides which process should be given access to the CPU based on the process’s priority level, but once a process has been given access to the CPU, it continues to run until it has completed or is blocked.

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Advantages of Non-Preemptive Scheduling

  • Lower overhead from context switching, leading to better system performance.
  • Processes that require long periods of uninterrupted CPU time can be efficiently processed.

Disadvantages of Non-Preemptive Scheduling

  • Low-priority processes may hog the CPU for an extended period, leading to decreased system responsiveness.
  • Poor utilization of CPU time if processes that require short periods of CPU time are repeatedly added to the system.

Differences between Preemptive and Non-Preemptive Scheduling

  1. n preemptive scheduling, a running process can be interrupted by a higher-priority process at any time. In non-preemptive scheduling, a process continues to run until it voluntarily relinquishes the CPU or is blocked by an I/O request.
  2. Preemptive scheduling can cause frequent context switching, which can impact system performance. Non-preemptive scheduling has lower overhead from context switching.
  3. Preemptive scheduling provides higher system responsiveness but can cause some processes to be starved of CPU time if higher-priority processes are continuously being added to the system. Non-preemptive scheduling provides better system performance but may lead to poor utilization of CPU time.

Conclusion

In conclusion, preemptive and non-preemptive scheduling are two different approaches used by operating systems to manage processes. Preemptive scheduling provides higher system responsiveness but can cause overhead from context switching and starve some processes of CPU time. Non-preemptive scheduling has lower overhead from context switching and provides better system performance, but low-priority processes may hog the CPU for an extended period. The choice between the two depends on the specific requirements of the system and the trade-offs between system responsiveness and performance.