Difference Between Preemptive and Non-Preemptive Scheduling in OS (Full Detail)

Preemptive scheduling is a CPU scheduling method that allocates certain amounts of CPU time to specific interactions. However, with non-preemptive scheduling, the cycle takes the resource (CPU time) and retains it until the interaction is terminated or moved to the holding upstate. Preemptive processes have costs attached to them, but non-preemptive processes don’t.

Let’s compare the features of preemptive and non-preemptive scheduling and then briefly analyze their differences using the comparison chart below.

Preemptive Vs Non preemptive scheduling

What is Preemptive Scheduling?

Preemptive scheduling is employed whenever a process transitions from the running state to the ready state or from the waiting state to the ready state. The resources, mostly CPU cycles, are given to the process for a set period of time before being removed; if the process still has CPU burst time left, it is then put back in the ready queue. Until it has its subsequent opportunity to run, the process remains in the ready queue.

Preemptive scheduling algorithms include Round Robin (RR), Shortest Remaining Time First (SRTF), Priority (preemptive version), etc.

Preemptive Scheduling

What is Non-Preemptive Scheduling?

Non-Preemptive Scheduling is the CPU operation that takes place when a process terminates or switches from an ongoing to a waiting for state.

When the operations are finished moving from one state to the next, this sort of scheduling is used. Since this type of procedure lacks the ability to halt operations like a preemptive one does, once it begins, it will continue uninterrupted until it is completed.

It usually happens because Non-Preemptive Scheduling does not allow for the function to pause an operation in the middle, forcing it to wait until the first operation is complete.

All things considered, it persists until the cycle completes its task, at which point it will be transmitted to the subsequent process.

The sole approach that may be used to various hardware stages. This is because it requires specialized equipment, such as precautionary Scheduling.

Since there is no technique for switching overhead operations in non-preemptive scheduling, the CPU must wait until the subsequent operation is transferred.

Due to the fact that it cannot be interrupted, non-preemptive scheduling is less flexible than preemptive scheduling.

Non-Preemptive Scheduling

Comparison Table (Preemptive vs Non-Preemptive Scheduling in OS)

 Basics of ComparisonPreemptive SchedulingNon-preemptive Scheduling
Flexibility flexible. on-flexible.
Cost It is cost-associated. It is non-cost associated.
Algorithm It uses an overhead switching algorithm.There is no such overhead switching algorithm in it.
Interruption The procedure is easily interruptible.The process cannot be interrupted.
CPU utilization More efficient Less efficient

Key Differences Between Preemptive and Non-Preemptive Scheduling

  • Preemptive scheduling allows for easy process interruption, whereas non-preemptive scheduling requires that the current cycle be completed before moving on to the following one.
  • Preemptive scheduling involves scheduling numerous operations, which adds overhead to the process. Non-preemptive scheduling doesn’t have this problem because it doesn’t have a function to handle interruptions to the process.
  • Preemptive scheduling, as opposed to non-preemptive scheduling, is flexible (i.e., easily modifiable) in nature.
  • In preemptive scheduling, the process with the highest priority is given precedence, whereas in non-preemptive scheduling, the current operation must be completed before moving on to the subsequent one.
  • Preemptive Scheduling is more affordable to use to conduct the process, however Non-Preemptive Scheduling is completely free.


What is the difference between preemptive and non-preemptive multitasking?

In contrast to non-preemptive multitasking, preemptive multitasking allows the operating system to take over the processor without the task’s consent. For example, in non-preemptive multitasking, a task may choose to give up its autonomy. Preemption is the process of removing control from a task.

What is preemptive and non-preemptive?

Preemptive and non-preemptive CPU scheduling are the two main categories. When a process switches from a running state to a ready state or from a waiting state to a ready state, this is known as preemptive scheduling. When a process ends or moves from a running to a waiting state, non-preemptive scheduling is used.

What is preemptive in operating system?

When referring to operating systems, the term “preemption” refers to the capacity of the operating system to preempt (that is, stop or pause) an already scheduled task in favor of a task having a higher priority. The CPU or I/O are just two examples of the resources that might be scheduled.


Preemptive scheduling is not superior to non-preemptive scheduling, and vice versa. Everything depends on how a schedule increases CPU utilization while minimizing the average waiting time of the processes.