Preemption

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.

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

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.