Hard periodic real-time task scheduling on mobile heterogeneous processor

High-performance heterogeneous processors are being implemented in mobile embedded real-time systems because of the increasing computational requirements. A heterogeneous processor consists of cores that are asymmetric in performance and functionality. Such a design provides a cost-effective solution for processor manufacturers to continuously improve both single-thread performance and multi-thread throughput. These complex processors have a major drawback when they are used for real-time purposes. Their complexity difficults the calculation of the worst case execution time (WCET). This design, however, faces significant challenges in the operating system (OS), which traditionally assumes only homogeneous hardware. The OS scheduler needs to be heterogeneity-aware, so it can match jobs to cores according to the characteristics of both. In this paper, we make a case that a scheduler for heterogeneous multicore (HMC) systems should target three objectives: optimal performance, minimum load and maximum satisfied deadline. We deal with this issue via optimal task-to-core assignment. The proposed scheduler enables performance improvements, reduction in load and satisfied deadline increase for range of applications. Different scheduling alternatives have been evaluated and experimental results show that the proposed algorithm provides, on average, improvement in our three objectives ranging from 5.34% to 8.75%.