On-the-fly fast overrun budgeting for mixed-criticality systems
Biao Hu, Kai Huang, Pengcheng Huang, Lothar Thiele, Alois Knoll · 2016
In mixed-criticality scheduling, the widely assumed mode-switch scheme assumes that both high- and low-criticality tasks are schedulable when no tasks overrun (normal mode) and all high-criticality tasks are schedulable even when they overrun (critical mode, where low-criticality tasks are abandoned/degraded). However, this scheme triggers a mode-switch immediately after any task overruns, which can be abrupt and pessimistic. In this paper, we tackle dual-criticality systems scheduled by earliest-deadline-first, and propose light-weight mode-switch schemes that are effective in keeping the system "away" from the critical mode. Our main idea is to perform overrun budgeting for all tasks as a whole, by monitoring task executions and updating a common overrun budget. This way, the overrun budget is shared among all tasks, and adaptively replenished leveraging run-time information; consequently, mode-switch can be postponed as much as possible. Experimental results demonstrate that the proposed mode-switch schemes outperform existing solutions to a large extent, in reducing the abandoned jobs and mode-switch frequencies, as well as in increasing the time ratio that all tasks are scheduled in the system.