172 research outputs found
A Modeling Framework for Schedulability Analysis of Distributed Avionics Systems
This paper presents a modeling framework for schedulability analysis of
distributed integrated modular avionics (DIMA) systems that consist of
spatially distributed ARINC-653 modules connected by a unified AFDX network. We
model a DIMA system as a set of stopwatch automata (SWA) in UPPAAL to analyze
its schedulability by classical model checking (MC) and statistical model
checking (SMC). The framework has been designed to enable three types of
analysis: global SMC, global MC, and compositional MC. This allows an effective
methodology including (1) quick schedulability falsification using global SMC
analysis, (2) direct schedulability proofs using global MC analysis in simple
cases, and (3) strict schedulability proofs using compositional MC analysis for
larger state space. The framework is applied to the analysis of a concrete DIMA
system.Comment: In Proceedings MARS/VPT 2018, arXiv:1803.0866
A Compositional Approach for Schedulability Analysis of Distributed Avionics Systems
This work presents a compositional approach for schedulability analysis of
Distributed Integrated Modular Avionics (DIMA) systems that consist of
spatially distributed ARINC-653 modules connected by a unified AFDX network. We
model a DIMA system as a set of stopwatch automata in UPPAAL to verify its
schedulability by model checking. However, direct model checking is infeasible
due to the large state space. Therefore, we introduce the compositional
analysis that checks each partition including its communication environment
individually. Based on a notion of message interfaces, a number of message
sender automata are built to model the environment for a partition. We define a
timed selection simulation relation, which supports the construction of
composite message interfaces. By using assume-guarantee reasoning, we ensure
that each task meets the deadline and that communication constraints are also
fulfilled globally. The approach is applied to the analysis of a concrete DIMA
system.Comment: In Proceedings MeTRiD 2018, arXiv:1806.09330. arXiv admin note: text
overlap with arXiv:1803.1105
Schedulability Analysis for Certification-friendly Multicore Systems
This paper presents a new schedulability test for safety-critical software undergoing a transition from single-core to multicore systems - a challenge faced by multiple industries today. Our migration model, consisting of a schedulability test and execution model, is distinguished by three aspects consistent with reducing transition cost. First, it assumes externally-driven scheduling parameters, such as periods and deadlines, remain fixed (and thus known), whereas exact computation times are not. Second, it adopts a globally synchronized conflict-free I/O model that leads to a decoupling between cores, simplifying the schedulability analysis. Third, it employs global priority assignment across all tasks on each core, irrespective of application, where budget constraints on each application ensure isolation. These properties enable us to obtain a utilization bound that places an allowable limit on total task execution times. Evaluation results demonstrate the advantages of our scheduling model over competing resource partitioning approaches, such as Periodic Server and TDMA.Ope
Analysis of Dynamic Memory Bandwidth Regulation in Multi-core Real-Time Systems
One of the primary sources of unpredictability in modern multi-core embedded
systems is contention over shared memory resources, such as caches,
interconnects, and DRAM. Despite significant achievements in the design and
analysis of multi-core systems, there is a need for a theoretical framework
that can be used to reason on the worst-case behavior of real-time workload
when both processors and memory resources are subject to scheduling decisions.
In this paper, we focus our attention on dynamic allocation of main memory
bandwidth. In particular, we study how to determine the worst-case response
time of tasks spanning through a sequence of time intervals, each with a
different bandwidth-to-core assignment. We show that the response time
computation can be reduced to a maximization problem over assignment of memory
requests to different time intervals, and we provide an efficient way to solve
such problem. As a case study, we then demonstrate how our proposed analysis
can be used to improve the schedulability of Integrated Modular Avionics
systems in the presence of memory-intensive workload.Comment: Accepted for publication in the IEEE Real-Time Systems Symposium
(RTSS) 2018 conferenc
Design of Energy-efficient Hierarchical Scheduling for Integrated Modular Avionics Systems
AbstractRecently the integrated modular avionics (IMA) architecture which introduces the concept of resource partitions becomes popular as an alternative to the traditional federated architecture. This study investigates the problem of designing hierarchical scheduling for IMA systems. The proposed scheduler model enables strong temporal partitioning, so that multiple hard real-time applications can be easily integrated into an uniprocessor platform. This paper derives the mathematic relationships among partition cycle, partition capacity and schedulability under the real-time condition, and then proposes an algorithm for optimizing partition parameters. Real-time tasks with arbitrary deadlines are considered for generality. To further improve the basic algorithm and reduce the energy consumption for embedded systems in aircraft, a power optimization approach is also proposed by exploiting the slack time. Experimental results show that the designed system can guarantee the hard real-time requirement and reduce the power consumption by at least 14%
Scheduling Based on Interruption Analysis and PSO for Strictly Periodic and Preemptive Partitions in Integrated Modular Avionics
Integrated modular avionics introduces the concept of partition and has been widely used in avionics industry. Partitions share the computing resources together. Partition scheduling plays a key role in guaranteeing correct execution of partitions. In this paper, a strictly periodic and preemptive partition scheduling strategy is investigated. First, we propose a partition scheduling model that allows a partition to be interrupted by other partitions, but minimizes the number of interruptions. The model not only retains the execution reliability of the simple partition sets that can be scheduled without interruptions, but also enhances the schedulability of the complex partition sets that can only be scheduled with some interruptions. Based on the model, we propose an optimization framework. First, an interruption analysis method to decide whether a partition set can be scheduled without interruptions is developed. Then, based on the analysis of the scheduling problem, we use the number of interruptions and the sum of execution time for all partitions in a major time frame as the optimization objective functions and use particle swarm optimization (PSO) to solve the optimization problem when the partition sets cannot be scheduled without interruptions. We improve the update strategy for the particles beyond the search space and round all particles before calculating the fitness value in PSO. Finally, the experiments with different partitions are conducted and the results validate the partition scheduling model and illustrate the effectiveness of the optimization framework. In addition, other optimization algorithms, such as genetic algorithm and neural networks, can also be used to solve the partition problem based on our model and solution framework
Heterogeneous models and analyses in the design of real-time embedded systems - an avionic case-study
The development of embedded systems according to Model-Driven Development relies on two complementary activities: system mod- eling on the one hand and analysis of the non-functional properties, such as timing properties, on the other hand. Yet, the coupling be- tween models and analyses remains largely disregarded so far: e.g. how to apply an analysis on a model? How to manage the analysis process? This paper presents an application of our research on this topic. In particular, we show that our approach makes it possible to combine heterogeneous models and analyses in the design of an avionic system. We use two languages to model the system at di erent levels of abstraction: the industry standard AADL (Ar- chitecture Analysis and Design Language) and the more recent implementation-oriented CPAL language (Cyber-Physical Action Language). We then combine di erent real-time scheduling analy- ses so as to gradually de ne the task and network parameters and nally validate the schedulability of all activities of the system
Real-time hierarchical systems with arbitrary scheduling at global level
[EN] Partitioned architectures isolate software components into independent partitions whose execution will not interfere with other partitions, preserving temporal and spatial isolation. Hierarchical scheduling can effectively be used to schedule these systems. Schedulability analysis of hierarchical real-time systems is based on prior knowledge of the local and the global scheduling algorithms.
In a partitioned system with safety and security issues and certification assurance levels, global scheduling is usually generated using a static table. Therefore, each partition must allocate task jobs only in the temporal windows reserved for that partition. Even if the static table can come originally from a periodic server or other scheduling policy, the final plan may be modified due to changes in the system requirements. As a consequence, the CPU assignment to a partition does not have to correspond to any known policy. In this case, it is not possible to use existing scheduling analysis for hierarchical systems.
This paper studies a new scheduling problem: a hierarchical system in which global policy is not known but provided as a set of arbitrary time windows.This work has been funded by the Spanish government under grant TIN2014-56158-C4-1-P-AR and by the European Commission under FP7-ICT-2013.3.4 Programme with grant 610640Guasque Ortega, A.; Balbastre, P.; Crespo, A. (2016). Real-time hierarchical systems with arbitrary scheduling at global level. Journal of Systems and Software. 119:70-86. https://doi.org/10.1016/j.jss.2016.05.040S708611
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