There exist garbage collection techniques suitable for interactive and soft real-time systems, but few algorithms are suitable for systems with hard real-time requirements, such as control systems (embedded systems). This thesis is focused on the scheduling problem, i.e. how the work of a garbage collector should be scheduled in order to disturb the application program as little as possible. It concentrates especially on control systems, i.e. embedded systems controlling some external physical process. In such systems, the hard real-time requirements are often isolated to a few high-priority software processes which execute periodically. A scheduling strategy is presented that employs this property to ensure that no garbage collection work is performed during the execution of the critical processes, thus not causing any disturbance.
The thesis shows how to adapt a standard incremental garbage collection algorithm to schedule its work according to the presented strategy. It is also discussed how to implement such a system by integrating the garbage collector with the process scheduler of the real-time kernel. Traditionally, garbage collection and process scheduling have been viewed as two separate issues.
The scheduling algorithm has been implemented in an actual real-time environment in order to show that the strategy is feasible in practice.