Schedulability Analysis of Adaptive Variable-Rate Tasks with Dynamic Switching Speeds

In real-time embedded systems certain tasks are activated according to a rotation source, such as angular tasks in engine control unit triggered whenever the engine crankshaft reaches a specific angular position. To reduce the workload at high speeds, these tasks also adopt different implementations at different rotation speed intervals. However, the current studies limit to the case that the switching speeds at which task implementations should change are configured at design time. In this paper, we propose to study the task model where switching speeds are dynamically adjusted. We develop schedulability analysis techniques for such systems, including a new digraph-based task model to safely approximate the workload from software tasks triggered at predefined rotation angles. Experiments on synthetic task systems demonstrate that the proposed approach provides substantial benefits on system schedulability.