Lecture 04: Context Switching and Dispatcher

1. The Dispatcher’s Role (Bridging Scheduler to CPU)
2. Process Scheduling Cycle (The Continuous Flow)
3. Context Switch Performance (Overhead & Optimization)
4. Degree of Multiprogramming (System Load & Performance)
5. Real-World Implementations (Linux vs. Windows)
6. Key Takeaways & Discussion

Slide Deck

Key Takeaways

• Context switching is the core mechanism that allows a single CPU to handle multiple processes by rapidly saving and restoring their execution states.
• The Dispatcher is the kernel component responsible for the actual context switch, mode switch, and jumping to the new process’s execution point.
• Dispatch latency and overall context switch overhead (direct and indirect, e.g., TLB/cache) are critical performance considerations in OS design.
• The degree of multiprogramming is a critical factor influencing system performance, affecting both CPU utilization and overhead.
• Thrashing is a severe performance degradation caused by an excessively high degree of multiprogramming, leading to constant paging.
• Different operating systems (like Linux and Windows) employ specific data structures and functions to optimize this crucial operation.