Process of saving and restoring process execution states
Context switching is the fundamental mechanism that enables multitasking in operating systems by allowing the CPU to switch between different processes. When a context switch occurs, the operating system saves the state of the currently running process (including register values, program counter, stack pointer, and other context information) and loads the saved state of another process to resume its execution. Context switches can be triggered by various events including hardware interrupts, system calls, scheduling timeouts, or when a process voluntarily yields the CPU. The process involves saving the current process's context to its Process Control Block (PCB), updating scheduling information, selecting the next process to run, loading the new process's context from its PCB, and updating memory management structures. Context switching overhead includes the time spent saving and restoring registers, flushing and repopulating CPU caches, and updating various kernel data structures. Modern processors provide hardware support for efficient context switching through features like multiple register sets and specialized instructions. Understanding context switching is crucial for system performance optimization, as excessive context switches can significantly impact system throughput and responsiveness, particularly in systems with many short-running processes or real-time constraints.