Scheduling garbage collection in real-time systems

The key to successful deployment of garbage collection in real-time systems is to enable provably safe schedulability tests of the real-time tasks. At the same time one must be able to determine the total heap usage of the system. Schedulability tests typically require a uniformed model of timing assumptions (inter-arrival times, deadlines, etc.). Incorporating the cost of garbage collection in such tests typically requires both artificial timing assumptions of the garbage collector and restricted capabilities of the task scheduler. In this paper, we pursue a different approach. We show how the reactive object model of the programming language Timber enables us to decouple the cost of a concurrently running copying garbage collector from the schedulability of the real-time tasks. I.e., we enable any regular schedulability analysis without the need of incorporating the cost of an interfering garbage collector. We present the garbage collection demand analysis, which determines if the garbage collector can be feasibly scheduled in the system.