Bringing theory into practice: A userspace library for multicore real-time scheduling

As multicore computing hardware has become more ubiquitous, real-time scheduling theory aimed at multicore systems has become increasingly sophisticated and diverse. Real-time operating systems (RTOSs) are ill-suited for this kind of rapid change, and the slow-moving RTOS ecosystem is falling further and further behind advances in real-time scheduling theory. Thus, supporting new functionality in a layer of middleware software running in userspace (i.e., outside the RTOS kernel) has been proposed. In this paper, we describe the first userspace scheduler that supports preemptive, dynamic-priority, migrating real-time tasks on multicore hardware, and report empirical latency and overhead measurements. On an eight-core Intel Xeon platform, these measurements are in the range of ones to tens of microseconds under most tested configurations. We believe that this approach may prove superior to a kernel-based approach for supporting a subset of future real-world realtime applications.