Non-Preemptive vs. Preemptive

Attribute	Non-Preemptive	Preemptive
Definition	Does not allow interruption of a process until it completes its execution	Allows interruption of a process by a higher priority process
Priority	Does not consider priority levels of processes	Considers priority levels of processes
Context Switching	Less frequent context switching	More frequent context switching
Complexity	Less complex to implement	More complex to implement

Introduction

When it comes to scheduling algorithms in operating systems, two common approaches are non-preemptive and preemptive scheduling. Both have their own set of attributes and advantages, which make them suitable for different scenarios. In this article, we will compare the attributes of non-preemptive and preemptive scheduling algorithms to understand their differences and similarities.

Non-Preemptive Scheduling

Non-preemptive scheduling, also known as cooperative scheduling, allows a process to run until it voluntarily gives up the CPU or completes its execution. In this approach, once a process starts running, it continues to run until it finishes or blocks for I/O. The operating system does not interrupt the process to give CPU time to another process. This type of scheduling is simpler to implement and has lower overhead compared to preemptive scheduling.

• Processes run to completion without interruption
• Lower overhead due to no context switching
• Simple implementation
• May lead to poor response time for interactive tasks
• Not suitable for time-sharing systems

Preemptive Scheduling

Preemptive scheduling, on the other hand, allows the operating system to interrupt a process and allocate CPU time to another process. This interruption can occur based on priorities, time slices, or other criteria defined by the scheduler. Preemptive scheduling ensures fairness and responsiveness in the system by preventing a single process from monopolizing the CPU for an extended period. However, it comes with higher overhead due to frequent context switches.

• Allows for fairness and responsiveness in the system
• Prevents a single process from monopolizing the CPU
• Higher overhead due to frequent context switches
• Complex implementation compared to non-preemptive scheduling
• Suitable for time-sharing systems and real-time applications

Comparison of Attributes

When comparing non-preemptive and preemptive scheduling algorithms, several attributes come into play. One of the key differences is in how they handle process execution. Non-preemptive scheduling allows a process to run to completion without interruption, while preemptive scheduling can interrupt a process to allocate CPU time to another process.

Another important attribute to consider is the overhead associated with each scheduling algorithm. Non-preemptive scheduling has lower overhead since there are no frequent context switches, while preemptive scheduling incurs higher overhead due to the need for context switches whenever a process is interrupted.

Furthermore, the responsiveness and fairness of the system are impacted by the choice of scheduling algorithm. Preemptive scheduling ensures fairness by preventing a single process from monopolizing the CPU, while non-preemptive scheduling may lead to poor response time for interactive tasks.

Additionally, the suitability of each scheduling algorithm for different types of systems is worth considering. Non-preemptive scheduling is simpler to implement and is suitable for systems where responsiveness is not critical, such as embedded systems. On the other hand, preemptive scheduling is more complex but is necessary for time-sharing systems and real-time applications where fairness and responsiveness are crucial.

Conclusion

In conclusion, both non-preemptive and preemptive scheduling algorithms have their own set of attributes and advantages. Non-preemptive scheduling is simpler to implement and has lower overhead, but it may lead to poor response time for interactive tasks. Preemptive scheduling, on the other hand, ensures fairness and responsiveness in the system but comes with higher overhead and complexity. The choice between the two scheduling algorithms depends on the specific requirements of the system and the trade-offs between simplicity, overhead, responsiveness, and fairness.