An Evaluation of Time-triggered Scheduling in the Linux Kernel

The GNU/Linux operating system (OS) is becoming more commonly used in real-time systems and has been modified with specific updates to provide faster and bounded response times as well as with fixed- and dynamic-priority real-time scheduling mechanisms. While the EDF-based scheduler ensures deadlines and temporal isolation for real-time tasks, it may not provide the level of determinism needed for modern applications that also have to consider complex jitter and multi-rate task dependencies. In this paper, we propose, implement, and evaluate an open-source, kernel-level time-triggered scheduling approach for Linux, examining the level of determinism achievable in terms of task execution and end-to-end latencies. We show that time-triggered scheduling in the Linux kernel achieves reduced latency and jitter for real-time applications when compared to the existing scheduling policies and user-space time-triggered implementations. Additionally, in terms of end-to-end communication latencies for distributed real-time applications, we compare a software-based IEEE 802.1Qvb time-aware gating implementation for time-sensitive networking (TSN) in which the time-triggered application schedule can be aligned to the network schedule to the standard Linux networking subsystem.