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Context switch

A context switch is the computing process of storing and restoring the state of a CPU (the context) such that multiple processes can share a single CPU resource. The context switch is an essential feature of a multitasking operating system. Context switches are usually computationally intensive and much of the design of operating systems is to optimize the use of context switches.

Context switches usually involve the following steps, assuming process P1 is running on the CPU and process P2 is the next process to run on the CPU:

Some CPUs contain logic to allow several hardware contexts to simultaneously exist, eliminating the need to store and restore the CPU context to memory on context switch.