context switch


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context switch

[′kän‚text ‚swich]
(computer science)
The action of a central processing unit that suspends work on one process to work on another.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

context switch

(operating system)
When a multitasking operating system stops running one process and starts running another. Many operating systems implement concurrency by maintaining separate environments or "contexts" for each process. The amount of separation between processes, and the amount of information in a context, depends on the operating system but generally the OS should prevent processes interfering with each other, e.g. by modifying each other's memory.

A context switch can be as simple as changing the value of the program counter and stack pointer or it might involve resetting the MMU to make a different set of memory pages available.

In order to present the user with an impression of parallism, and to allow processes to respond quickly to external events, many systems will context switch tens or hundreds of times per second.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)
References in periodicals archive ?
To guarantee the universality, we adopt the standard Crypto API framework in kernel for the invocation of hardware accelerators, which includes the overhead for Mode Switch and Context Switch. The detailed processing steps and overhead are concluded as follows:
However, the possibility of information leakage attributed to a context switch from [[tau].sub.L] to [[tau].sub.H] should not be ignored because the change of execution state can also compromise the security of the RTS.
A software thread maps directly onto a TU and the execution is nonpreemptive; that is, the microkernel will not interrupt the execution of a user application unless an exception occurs (no context switch).
However, comparing mean changes in magazine approaches of groups T-FT30-A and T-FT30-B at the first trial of the last acquisition session [(10.11 [+ or -] 4.00) and (12.27 [+ or -] 3.86), respectively], and at the first trial of the first extinction session [(1.59 [+ or -] 2.16) and (4.56 [+ or -] 2.31), respectively] only found a significant main effect of Session, F(1, 12) = 23.59, MSe = 19.23, [[eta].sup.2] = 0.663, p < 0.001, showing that the context switch between acquisition and extinction did not have detectable effects on performance.
Partial reinforcement and context switch effects in human predictive learning.
Whether the test context is familiar at the time of testing does not seem to be a key factor on context specificity either, given that context switch effects on taste aversion learning have been reported with familiar contexts in some occasions (e.g., Bonardi et al., 1990) but not in others (e.g., Rosas & Bouton, 1997, 1998; Rosas et al., 2007).
For example, on the Advantech PCM-9386 the worst case context switch from real-time thread to real-time thread is 5.8 microseconds.
In preemptive mode, the timer ISR also acts as a task dispatcher: it saves the current execution context on the stack and, if a context switch is required, it checks if a higher priority task has been reactivated.
These authors found a context switch effect after partial reinforcement using a predictive learning task with human subjects in which participants had to predict whether different kinds of foods would produce a gastric malaise in people who ate at one of two different restaurants (see, for instance, Garcia-Gutierrez & Rosas, 2003).

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