TaskPair-scheduling with optimistic case execution times-an example for an adaptive real-time system

The paper first describes a model for an adaptive real time system, that consists of four components: the real time application, a monitor that observes the behaviour of the application, a dynamic resource manager that controls the execution of the application based on the data collected by the monitor, and finally an adaptation manager that uses the input from the monitor to implement long term adaptation strategies. In the second part of the paper, a concrete adaptation mechanism is introduced. This mechanism extends TaskPair scheduling (H. Streich, 1995), an online, fault tolerant scheduling method developed at GMD within the context of the DIRECT project (M. Gergeleit et al., 1994). TaskPair scheduling is extended with the notion of optimistic case execution time (OCET), that describes the time that a task needs in most of the cases for successful completion. As this time may depend on the system state and the environment, the system observes the actual resource consumption during execution and adapts future resource requests accordingly.

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