Clockwerk: A Predictable and Efficient Extension of Logical Execution Time Model

Real-time systems focus on achieving fast response time, which, however, is usually accompanied by sacrificing the predictability. The Logical Execution Time (LET) model achieves I/O-predictability by fixing the timing of reading inputs and writing outputs. However, LET lacks the mechanism to react to aperiodic requests which have frequently been used in soft real-time applications. To improve aperiodic responsiveness as well as obtain predictability, in this paper, we present a component-based LET extension-Clockwerk. Clockwerk introduces the concept of Servant as basic components to make both communication and computation parts of periodic tasks predictable. By combining the LET model with the aperiodic server, Clockwerk achieves the improvement of aperiodic responsiveness. Consequently, our proposal can reduce the complexity of schedulability analysis on periodic tasks to polynomial time, and preliminary simulation results show that it also achieves an aperiodic responsiveness speedup of 4.1X-6.5X compared with existing work.