Preemptive vs. Non-Preemptive Scheduler

Topics: Embedded Systems

Preemptive

A preemptive scheduler may interrupt the current task to dispatch another task that typically requires a higher priority.

Advantages

• Distributes resources better, so one processes cannot hog CPU
• Can help meet deadlines better in hard real-time

Disadvantages

• More complex to implement
• Higher context switching overhead
• High priority tasks might utilize most of CPU
• Concurrency issues when using mutexes and semaphores

Non-Preemptive

In a non-preemptive scheduler, the current task runs until it finishes before another task is dispatched.

Advantages

• Simpler to implement
• Low scheduling and context switching delay

Disadvantages

• One long-running task can occupy all CPU
• Average response time is higher

References

1. https://industrialmonitordirect.com/blogs/knowledgebase/preemptive-vs-non-preemptive-scheduling-in-rtos-explained?srsltid=AU7gw4UT8dnUMYSSxHxRECKxzdM4c5WQVZUOTU_j1iFhDpz-FXWixrbF
2. https://www.geeksforgeeks.org/operating-systems/preemptive-and-non-preemptive-scheduling/