Proportional - Share Scheduling of Aperiodic Requests under the Rate - Based Execution Model ∗

The rate-based execution (RBE) task model was developed to support the real-time execution of eventdriven tasks in which no a priori characterization of the actual arrival rates of events is known; only the expected arrival rates of events is known. The RBE model is well suited for systems that must execute in environments that are not well-behaved (i.e., when the arrival rate of events is neither periodic nor sporadic). Aperiodic requests with unknown execution times and unknown arrival patterns are mapped to RBE tasks and scheduled such that the real-time tasks are guaranteed to meet their deadlines while aperiodic requests share the available processor capacity without reserving a fixed processor capacity for any one aperiodic request. This approach was selected over the traditional approach of using a server task to process aperiodic requests so that the available processor capacity could be dynamically shared between active aperiodic requests.