The high computational complexity required for performing an exact schedulability analysis of fixed priority systems has led the research community to investigate new feasibility tests which are less complex than exact tests, but still provide a reasonable performance in terms of acceptance ratio. The performance of a test is typically evaluated by generating a huge number of synthetic task sets and then computing the fraction of those that pass the test with respect to the total number of feasible ones. The resulting ratio, however, depends on the metrics used for evaluating the performance and on the method for generating random task parameters. In particular, an important factor that affects the overall result of the simulation is the probability density function of the random variables used to generate the task set parameters. In this paper we discuss and compare three different metrics that can be used for evaluating the performance of schedulability tests. Then, we investigate how the random generation procedure can bias the simulation results of some specific scheduling algorithm. Finally, we present an efficient method for generating task sets with uniform distribution in a given space, and show how some intuitive solutions typically used for task set generation can bias the simulation results.

/pdf/measuring-the-performance-of-schedulability-tests-yr1og35xbk.pdf

Measuring the Performance of Schedulability Tests

Holistic schedulability analysis for distributed hard real-time systems

Cyber-physical systems (CPSs) are the next generation of engineered systems in which computing, communication, and control technologies are tightly integrated. Research on CPSs is fundamentally important for engineered systems in many important application domains such as transportation, energy, and medical systems. We overview CPS research from both a historical point of view in terms of technologies developed for early generations of control systems, as well as recent results on CPSs in many relevant research domains such as networked control, hybrid systems, real-time computing, real-time networking, wireless sensor networks, security, and model-driven development. We outline the potential for CPSs in many societally important application domains.

http://cesg.tamu.edu/wp-content/uploads/2012/03/ps_files/12-02-10-CPS-Centennial.pdf

Cyber–Physical Systems: A Perspective at the Centennial

As the real-time computing industry moves away from static cyclic executive-based scheduling towards more flexible process-based scheduling, so it is important for current scheduling analysis techniques to advance and to address more realistic application areas. This paper extends the current analysis associated with static priority pre-emptive based scheduling; in particular it derives analysis for tasks with arbitrary deadlines that may suffer release jitter due to being dispatched by a tick driven scheduler. We also consider bursty sporadic activities, where tasks arrive sporadically but then execute periodically for some bounded time. The paper illustrates how a window-based analysis technique can be used to find the worst-case response time of a task set, and shows that the technique can be easily extended to cope with realistic and complex task characteristics.

An extendible approach for analyzing fixed priority hard real-time tasks

Calculating controller area network (can) message response times

The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher. The tasks to be scheduled are allowed to experience internal blocking (from other tasks with which they share resources) and (with certain restrictions) to release jitter, such as waiting for a message to arrive. The analysis presented is more general than that previously published and subsumes, for example, techniques based on the Rate Monotonic approach. In addition to presenting the relevant theory, an existing avionics case study is described and analysed. The predictions that follow from this analysis are seen to be in close agreement with the behaviour exhibited during simulation studies.

https://www.math.unipd.it/~tullio/RTS/2009/ABRTW-1993.pdf

Mike M. Richardson

Papers

Applying new scheduling theory to static priority pre-emptive scheduling