In computer science preemption means the ability to withdraw a resource from its owner before the owner gives it up voluntarily. Most often this resource is the processor and the owner a task or process but also complete devices can be a resource (cf. HAVi's preemption scheme).

The ability to preempt has important consequences for deadlock prevention and available process scheduling strategies. The later are therefore often divided into preemptive and non-preemptive ones. Round-Robin is a preemptive strategy and Shortest Job First is the optimal non-preemptive strategy with respect to responsiveness. The optimal preemptive strategy is left as an exercise for the reader.

Pre*emp"tion (?; 215), n. [Pref. pre- + emption: cf. F. pr'eemption. See Redeem.]

The act or right of purchasing before others.

Specifically: (a)

The privilege or prerogative formerly enjoyed by the king of buying provisions for his household in preference to others.

[Eng.] (b)

The right of an actual settler upon public lands (particularly those of the United States) to purchase a certain portion at a fixed price in preference to all other applicants.



© Webster 1913.

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