This paper presents an automatic approach to synthesizing schedulable timing constraints for real-time control systems. Given the performance speci cations and schedulability constraints of a real-time control system, the approach derives task-level timing constraints which can guarantee these requirements. The control performance is speci ed in terms of control output responses such as steady state error, maximum overshoot, settling time, and rise time, and the task-level timing constraints include task periods and deadlines. The approach consists of two components with a clean interface. The rst component translates the performance speci cations into a set of system-level timing constraints such as loop processing periods and input-to-output latency, via control theoretic modeling and optimization. The second then derives task-level timing constraints from the intermediate system-level timing constraints optimizing the system schedulability using period calibration method 4, 17, 9]. Our approach contributes to both the control and real-time areas: (1) it allows control engineers to take into consideration the e ect of task scheduling at the early stage of system design; and (2) it makes it possible to streamline the design of real-time control systems, since timing constraints are derived in an automatic manner.

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In order to improve the performance of a real-time system, asymmetric multiprocessors have been proposed. The benefits of improved system performance and reduced power consumption from such architectures cannot be fully exploited unless suitable task scheduling and task allocation approaches are implemented at the operating system level. Unfortunately, most of the previous research on scheduling algorithms for performance asymmetric multiprocessors is focused on task priority assignment. They simply assign the highest priority task to the fastest processor. In this paper, we propose BSF-EDF (best speed fit for earliest deadline first) for performance asymmetric multiprocessor scheduling. This approach chooses a suitable processor rather than the fastest one, when allocating tasks. With this proposed BSF-EDF scheduling, we also derive an effective schedulability test.

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