Prototyping Hierarchically Scheduled Systems Using Task Automata and TIMES

David

Science of Computer Programming

et al. 2016

This paper contains two contributions: 1) A development methodology involving two techniques to enhance the resource utilization and 2) a new generic multi-core resource model for hierarchical scheduling systems. As the first contribution, we propose a two-stage development methodology relying on the adjustment of timing attributes in the detailed models during the design stage. We use a lightweight method (statistical model checking) for design exploration, easily assuring high confidence in the correctness of the models. Once a satisfactory design has been found, it can be proved schedulable using the computation costly method (symbolic model checking). In order to analyze a hierarchical scheduling system compositionally, we introduce the notion of a stochastic supplier modeling the supply of resources from each component to its child components in the hierarchy. We specifically investigate two different techniques to widen the set of provably schedulable systems: 1) a new supplier model; 2) restricting the potential task offsets. We also provide a way to estimate the minimum resource supply (budget) that a component is required to provide. In contrast to analytical methods, we prove nonschedulable cases via concrete counterexamples. By having richer and more detailed scheduling models this framework, has the potential to prove the schedulability of more systems. As the second contribution, we introduce a generic resource model for multi-core hierarchical scheduling systems, and show how it can be instantiated for classical resource models: Periodic Resource Models (PRM) and Explicit Deadline Periodic (EDP) resource models. The generic multi-core resource model is presented in the context of a compositional model-based approach for schedulability analysis of hierarchical scheduling systems. The multi-core framework presented in this paper is an extension of the single-core framework used for the analysis in the rest of the paper.

Section: Model-based Approaches To Schedulability Analysismentioning

confidence: 99%

“…Comp.id I(p, b) T (p, e) EDF RM C 1 (100, 33 (43)) T 1 (250, 40) 0.59 0.04 T 2 (400, 50) C 2 (150, 48 (48)) T 1 (250, 40) 0.89 0.01 T 2 (750, 50) C 3 (100, 34(39))T 1 (250,40) 7.53 0.01T 2 (450, 50) T 2 (750,35) Uppaal template ofFig. 9.…”

mentioning

confidence: 98%

Statistical and exact schedulability analysis of hierarchical scheduling systems

David

Science of Computer Programming

et al. 2016

“…Recent research within schedulability analysis gives tremendous attention to model-based approaches, because of their expressiveness that allows for modeling more complicated behavior of systems, and also due to the technological advances made in the area of modelbased simulation and analysis tools. In [4], the authors analyzed the schedulability of hierarchical scheduling systems using the TIMES tool [1,3], and implemented their model-based framework in VxWorks [4]. They constructed an abstract task model as well as scheduling algorithms focusing on the component under analysis.…”

Section: Related Workmentioning

confidence: 99%

Widening the Schedulability of Hierarchical Scheduling Systems

David

Formal Aspects of Component Software

et al. 2015

Abstract. This paper presents a compositional approach for schedulability analysis of hierarchical systems, which enables to prove more systems schedulable by having richer and more detailed scheduling models. We use a lightweight method (statistical model checking) for design exploration, easily assuring high confidence in the correctness of the model. A satisfactory design can be proved schedulable using the computation costly method (symbolic model checking). In order to analyze a hierarchical scheduling system compositionally, we introduce the notion of a stochastic supplier modeling the supply of resources in each component. We specifically investigate two different techniques to widen the set of provably schedulable systems: 1) a new supplier model; 2) restricting the potential task offsets. We also provide a way to estimate the minimum resource supply (budget) that a component is required to provide.

“…If such an equation is satisfied, the component is said to be schedulable. In the same way, in a model-based setting [28,2,10,4] a system is said to be schedulable if the error locations, stating the deadline violation, are unreachable. Moreover, in our model-based framework, the condition dbfA(W, t) ≤ sbfI(t) is applied not only to EDF but also for other scheduling policies, such as FP scheduling, so that the same task models are able to be used for different scheduling policies.…”

Section: Compositional Frameworkmentioning

confidence: 99%

Quantitative Schedulability Analysis of Continuous Probability Tasks in a Hierarchical Context

Proceedings of the 18th International ACM SIGSOFT Symposium on Component-Based Software Engineering

Nyman

et al. 2015

We define the concept of degree of schedulability to characterize the schedulability and performance of soft real-time systems. The degree of schedulability of a system is given in terms of the two factors 1) Percentage of Missed Deadlines (PoMD); and 2) Degradation of the Quality of Service (DoQoS). Our work is set as a model-based framework for hierarchical scheduling systems where we introduce probability based sporadic tasks. The novel aspect is that we consider task arrival patterns that follow user-defined continuous probability distributions. The separately modeled task triggering events represent the system environment. We determine the degree of schedulability of a single scheduling component which can contain both periodic and sporadic tasks using statistical model checking in the form of Uppaal SMC. Finally, we show the applicability of our framework by analyzing an avionics case study.