Integrating best-effort scheduling into a real-time system

Demand for real-time capability in general-purpose systems is rising and as systems are retrofitted with scheduling features they become increasingly complex. To counter this trend we present the best-effort bandwidth server (BEBS), an aperiodic server for flexible and efficient support of best-effort applications in a real-time system. Recognizing that the responsiveness of a server depends on its period, and that not every best-effort task requires equal responsiveness, the algorithm adjusts its period based on run-time behavior of tasks. We created a prototype implementation of the system to demonstrate that it performs suitably as a general-purpose scheduler in comparison to Linux, and outperforms a common type of hierarchy used in existing general-purpose systems. The result is a system that integrates real-time scheduling with best-effort support, both simple and powerful enough to be used as the only scheduler in a general-purpose operating system.