This negatively affects performance because every memory reference to the TLB will be a miss because it is empty after most context switches. To avoid incorrect address translation in the case of the previous and current processes using different memory, the translation lookaside buffer (TLB) must be flushed. CPU state information including the registers, stack pointer, and program counter as well as memory management information like segmentation tables and page tables (unless the old process shares the memory with the new) are loaded from the PCB for the new process. What is actually involved in a context switch depends on the architectures, operating systems, and the number of resources shared (threads that belong to the same process share many resources compared to unrelated non-cooperating processes).įor example, in the Linux kernel, context switching involves loading the corresponding process control block (PCB) stored in the PCB table in the kernel stack to retrieve information about the state of the new process. Switching from one process to another requires a certain amount of time for doing the administration – saving and loading registers and memory maps, updating various tables and lists, etc. : 28Ĭontext switches are usually computationally intensive, and much of the design of operating systems is to optimize the use of context switches. The process of context switching can have a negative impact on system performance.

Some operating systems also require a context switch to move between user mode and kernel mode tasks. A context switch can also occur as the result of an interrupt, such as when a task needs to access disk storage, freeing up CPU time for other tasks. In a multitasking context, it refers to the process of storing the system state for one task, so that task can be paused and another task resumed. The precise meaning of the phrase 'context switch' varies. This allows multiple processes to share a single central processing unit (CPU), and is an essential feature of a multitasking operating system. In computing, a context switch is the process of storing the state of a process or thread, so that it can be restored and resume execution at a later point, and then restoring a different, previously saved, state. ( October 2017) ( Learn how and when to remove this template message)

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