HAPI: An event-driven simulator for real-time multiprocessor systems

Many embedded multiprocessor systems have hard real-time requirements which should be guaranteed at design time by means of analytical techniques that cover all cases. It is desirable to evaluate the correctness and tightness of the analysis results by means of simulation. However, verification of the analytically obtained results is hampered by the lack of a fast high level simulation approach that supports task scheduling and that does not produce pessimistic simulation traces. In this paper we present HAPI, an event driven simulator for the evaluation of the results of real-time analysis techniques for task graphs executed on multiprocessor systems that support processor sharing. HAPI produces simulation traces that are pessimistic to reality and optimistic to temporal analysis. It can be consequently used to detect optimistic, i.e. incorrect, analysis results. Several task scheduling policies are supported by HAPI such as fixed priority preemptive, time-division multiplex and round-robin. Preemptive task scheduling decisions are simulated which enables to study the cause of delayed task finishes and thereby helps to identify overly pessimistic analysis results. We demonstrate the applicability of the simulator using a number of didactic examples and a WLAN 802.11p application.