Efficient Mode Changes in Multi-Mode Systems

Multi-mode systems work in configurations, but face the challenge of ensuring timing guarantees during mode changes. In a multi-mode system, a mode-change request occurs when the system wants to operate in a new mode, but is already running in one. One mode may include some tasks that are same as that of another mode. Therefore, the new mode may have tasks that are same as the old mode. Changing modes in such a way to skip some already completed tasks can decrease the workload of the new mode. Traditional protocols for changing modes always look forward in time to schedule tasks, although using already completed tasks may avoid re-executing them in the new mode. Reusing common tasks reduces the time to re-execute them while switching modes. In this paper, we introduce the concept and design considerations for a mode-change technique that may use completed tasks stored in checkpoints to avoid unnecessary re-execution and facilitate faster execution of new mode tasks. Through an example case-study, experimental results demonstrate that the overhead of using checkpoints is low, and using rollback facilitates faster execution of new mode tasks if completed tasks stored in checkpoints can be reused.