Exploiting Aperiodic Server to Improve Aperiodic Responsiveness for LET-Based Real-Time Systems

摘要

Real-time systems often have to satisfy stringent timing constraints. However, to fully utilize system resources for the increasing needs of soft real-time applications, real-time systems are always designed to improve average-case performance instead of achieving predictability. Timing behaviors of systems become difficult to be inferred due to non-deterministic interleaves among concurrent tasks, especially when systems react to unexpected aperiodic requests. In this paper, we propose a component-based execution model, namely Clockwerk, to improve predictability as well as aperiodic responsiveness in real-time systems. Clockwerk extends LET to support the aperiodic tasks by Servants, which propose to implement the program component and runtime scheduling unit. A modified aperiodic server algorithm is applied to enhance the aperiodic responsiveness with no loss of predictability. A prototype of Clockwerk runtime system implements based on a mixture scheduler. We evaluate the implementation by a set of simulated and experimental evaluations. Evaluation results show that the aperiodic responsiveness of Clockwerk obtains 7.7X-16.7X speedup over a conventional work. And low overheads of our implementations demonstrate that Clockwerk is qualified to construct predictable real-time systems as well.