Catching two rabbits: Adaptive real-time support for embedded Linux

The trend of digital convergence makes multitasking common in many digital electronic products. Some applications in those systems have inherent real-time properties, while many others have few or no timeliness requirements. Therefore the embedded Linux kernels, which are widely used in those devices, provide real-time features in many forms. However, providing real-time scheduling usually induces throughput degradation in heavy multitasking due to the increased context switches. Usually the throughput degradation becomes a critical problem, since the performance of the embedded processors is generally limited for cost, design and energy efficiency reasons. This paper proposes schemes to lessen the throughput degradation, which is from real-time scheduling, by suppressing unnecessary context switches and applying real-time scheduling mechanisms only when it is necessary. Also the suggested schemes enable the complete priority inheritance protocol to prevent the well-known priority inversion problem.We evaluated the effectiveness of our approach with open-source benchmarks. By using the suggested schemes, the throughput is improved while the scheduling latency is kept same or better in comparison with the existing approaches.