Difference Between Preemptive and Non-Preemptive Scheduling in OS

In this post, we will understand the difference between pre-emptive and non-pre-emptive scheduling in operating system −

Preemptive scheduling

• In this type of scheduling, the resources (CPU Cycle) have been allocated to a process for a limited amount of time.

• A process can be interrupted when it is being executed.

• If a process that has a high priority arrives frequently in the ‘ready’ queue, the low priority processes may starve.

• This kind of scheduling has overheads since it has to schedule multiple processes.

• It is flexible in nature.

• It is expensive in nature.

• The CPU utilization is high in this type of scheduling.

• Examples of pre-emptive scheduling include: Round Robin scheduling, Shortest Remaining Time First scheduling.

Non-preemptive scheduling

• In this type of scheduling, once the resources (CPU Cycle) have been allocated to a process, the process holds it until it completes its burst time or switches to the ‘wait’ state.

• A process can’t be interrupted until it terminates itself or its time is over.

• If a process that has a long burst time is running the CPU, then the process that has less CPU burst time would starve.

• It doesn’t have overhead.

• It is not flexible in nature.

• It is not expensive in nature.

• Examples of non-pre-emptive scheduling include: First Come First Serve and Shortest Job First.