Pre-emptive Kernels

A pre-emptive kernel is a type of operating system kernel that allows a higher-priority process to interrupt a lower-priority process during execution. This means that if a higher-priority process becomes ready to execute, the kernel can interrupt the lower-priority process and allocate the CPU to the higher-priority process.

How Pre-emptive Kernels Work

In a pre-emptive kernel, each process is assigned a priority level, which determines its position in a queue of processes waiting for CPU time. The kernel constantly monitors the system for the arrival of new processes and the completion of existing processes. When a process completes, the kernel selects the next process to run based on its priority level.

If a higher-priority process becomes ready to run while a lower-priority process is running, the kernel can interrupt the lower-priority process and allocate the CPU to the higher-priority process. The kernel then saves the state of the interrupted process so that it can resume execution when it next receives CPU time.

Advantages of Pre-emptive Kernels

• Improved responsiveness: With pre-emptive kernels, higher-priority processes can be executed immediately, improving system responsiveness.
• Better resource utilization: Pre-emptive kernels can make better use of system resources by ensuring that higher-priority processes are given access to the CPU when needed.
• Increased stability: Pre-emptive kernels can improve system stability by preventing lower-priority processes from monopolizing system resources and causing system failures.
• Support for multitasking: Pre-emptive kernels support multitasking, allowing multiple processes to run concurrently.

Disadvantages of Pre-emptive Kernels

• Increased overhead: Pre-emptive kernels can incur higher overhead compared to non-pre-emptive kernels due to the need to constantly monitor and switch between processes.
• Potential for priority inversion: Priority inversion can occur when a high-priority process is blocked by a lower-priority process, leading to decreased system performance.
• Complexity: Pre-emptive kernels can be more complex to implement and manage compared to non-pre-emptive kernels.

Examples of Pre-emptive Kernels

Examples of operating systems that use pre-emptive kernels include:

• Linux
• Windows
• macOS
• Unix
• FreeBSD
• NetBSD

Conclusion

Pre-emptive kernels offer several advantages over non-pre-emptive kernels, including improved system responsiveness, better resource utilization, increased stability, and support for multitasking. However, they also come with certain disadvantages, such as increased overhead, potential for priority inversion, and complexity. Overall, pre-emptive kernels are widely used in modern operating systems and have become an essential component of many critical computing systems.