StateOS: A Memory-Efficient Hybrid Operating System for IoT Devices

The increasing significance of operating systems (OSs) in the development of the Internet of Things (IoT) has emerged in the last decade. An event-driven OS is memory efficient and suitable for resource-constrained IoT devices and wireless sensors, although the program’s control flow, which is determined by events, is not always obvious. A multithreaded OS with sequential control flow is often considered clearer. However, this approach is memory consuming. A hybrid OS seeks to combine the strengths of the event-driven approach with multithreaded approach. An event-driven cooperative threaded OS represents a hybrid approach that supports concurrency by explicitly yielding control to another thread. Although this approach is memory efficient, as cooperative threads are not preemptive, it may not provide sufficient real-time performance. This article proposes a memory-efficient hybrid OS, called StateOS, for resource-constrained IoT devices. It is an event-driven cooperative threaded OS with partial real-time performance. StateOS implements a hybrid task scheduler that combines two cooperative threaded subsystems as kernel processes on a priority-based preemptive scheduler. This approach provides adequate real-time performance for IoT devices at a low memory cost.