It is always useful to start with a simple example that contains the properties that we want to focus on. On this airbag video:
it is possible to see two airbags: one that inflates at the proper timing and another that deploys late. This represents the character of a Cyber-Physical System that needs to execute the steps correctly (infate the airbag) and execute them at the proper time in sync with the physical process (the driver traveling towards the steering wheel in a crash).
Zero-Slack Scheduling is a scheduling framework for real-time mixed-criticality systems. Specifically, it targets systems where the utilization-based scheduling priorities are not aligned with the criticality of the tasks. With this framework we implemented a family of schedulers, resource allocation protocols, and synchronization protocols to support the scheduling of mixed-criticality systems.
Zero-Slack Q-RAM combines ZS-RM and Q-RAM to enable overbooking (cycles allocated to more than one task) not only between tasks of different criticality but also to task with different utility to the mission of the system.We implemented three version of the ZS-QRAM scheduler: a modification to the Linux/RK kernel (and kernel module), an independent kernel module implementation, and a daemon-based implementation.
We developed a number of experiments to showcase the effects of the scheduler in a drone mission. In particular, first we demonstrate how the wrong scheduling can actually crash a drone. This is shown in this video.
Secondly, we showcase how in a full mission ZS-QRAM not only preserve the saftey of the flight but also maximizes the utility of the mission. In particular, the demo shows a surveillance mission where a video-streaming task and an object recognition tasks are dynamically adjusted according to their utility to the mission. This video shows this case.
Download Scheduler ImplementationsTo access both the kernel and kernel module implementations, please go to our Drone RK site.
To access the daemon-based scheduler click here.
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