Evaluation and comparison of integer programming solvers for hard real-time scheduling

[EN] In order to obtain a feasible schedule of a hard real-time system, heuristic based techniques are the solution of choice. In the last few years, optimization solvers have gained attention from research communities due to their capability of handling large number of constraints. Recently, some works have used integer linear programming (ILP) for solving mono processor scheduling of real-time systems. In fact, ILP is commonly used for static scheduling of multiprocessor systems. However, two main solvers are used to solve the problem indistinctly. But, which one is the best for obtaining a schedulable system for hard real-time systems? This paper makes a comparison of two well-known optimization software packages (CPLEX and GUROBI) for the problem of finding a feasible schedule on monoprocessor hard real-time systems.This work was supported under Grant PLEC2021-007609 funded by MCIN/AEI/10.13039/501100011033 and by the "European Union NextGeneration EU/PRTR"Guasque Ortega, A.; Balbastre, P. (2022). Evaluation and comparison of integer programming solvers for hard real-time scheduling. IEICE Transactions on Information and Systems. E105-D(10):1726-1733. https://doi.org/10.1587/transinf.2022EDP707317261733E105-D1

Procedimiento de diseño para minimizar el consumo de potencia y los retrasos en WSAN

ResumenActualmente existe un gran interés por el desarrollo de aplicaciones industriales utilizando redes inalámbricas, principalmente por el aumento de la flexibilidad del sistema y la disminución de los costos de implementación. Sin embargo, los retrasos y el jitter que introduce la red de comunicaciones en las aplicaciones de control, han dado lugar a que en algunos casos no se obtenga una buena correspondencia entre los resultados experimentales y los objetivos de control propuestos, esto como consecuencia del uso de modelos imprecisos para analizar y diseñar estos sistemas, métodos de validación poco elaborados y plataformas que no soportan los modelos empleados. En este trabajo se presenta un procedimiento de diseño que permite encontrar un modo de funcionamiento óptimo del sistema, que garantiza el cumplimiento de los plazos de tiempo de las aplicaciones, y minimiza el consumo de potencia y los retrasos

Jitter Evaluation of Real-Time Control Systems

The implementation of industrial control applications typically introduces complexities like sampling jitter and control jitter, which have usually not been considered at the design stage. Consequently, the system behaves in a non-periodic manner and the real performance is degraded with regard to the expected response. This paper proposes a hybrid task model to reduce the impact of the scheduling on control performance. For a large batch of typical plants, we analyze how sensitive a control system is to jitter when the sampling rate is slow or fast compared to the bandwidth of the system

Planificación multinúcleo en sistemas particionados

[Resumen] Actualmente, las aplicaciones embebidas se consideran de complejidad creciente y, como consecuencia, de mayor dificultad para su desarrollo y validación. Debido a estas características, existe un gran interés en ejecutar múltiples aplicaciones sobre una única plataforma (mono o multinúcleo). En los sistemas de tiempo real, cada vez más se ejecutan aplicaciones con diferentes niveles de criticidad donde múltiples componentes con diferentes restricciones de tiempo real se integran en una misma plataforma computacional. Al mismo tiempo en el que proliferan los sistemas de criticidad mixta, la plataforma computacional está migrando de mono núcleo a multinúcleo. El presente trabajo describe la planificación de sistemas particionados multinúcleo, desde la asignación de tareas a núcleos hasta la generación de la planificación para cada procesador.Este articulo ha sido subvencionado por el Ministerio de Economía y Competitividad bajo los proyectos TIN2014-56158-C4-1-P y TIN2014-56158-C4-4-Phttps://doi.org/10.17979/spudc.978849749808

Xoncrete: a scheduling tool for partitioned real-time systems

International audienceARINC 653 defines a partitioned framework where the partitions are scheduled according to a predefined cyclic plan and the processes of each partition are scheduled with a fixed priority policy. The timing characteristics defined in ARINC (period and duration) can hardly be used to precisely represent the timing requirements of the applications. We extend the timing model of ARINC 653 to consider deadlines and the periodic behaviour of the individual processes. A novel definition of how to model periodic activities and how this new model is specially useful in an heterogeneous partitioned system is also presented. The new model and the set of scheduling algorithms have been implemented in a scheduling tool (called Xoncrete) to assist the designer to generate the cyclic plan table. Although founded on solid theoretical results, Xoncrete is not a general purpose tool, it is a tool designed to provide real help to the system designer

La importancia del uso de procesos físicos reales en la enseñanza universitaria de la ingeniería

Este artículo revisa nuestra experiencia en el uso de procesos reales en la enseñanza universitaria. En concreto describe los resultados obtenidos en un grupo de asignaturas basadas en los Sistemas de Tiempo Real, las cuales se imparten en varias escuelas de la Universidad Politécnica de Valencia. El hecho de impartir estas asignaturas en diversas titulaciones permite, en cierta forma, generalizar los beneficios que aportan los procesos físicos reales en el ámbito universitario con los resultados de una asignatura

Experiencia docente en el desarrollo de aplicaciones empotradas con MarteOS

Este trabajo presenta la experiencia de realizar trabajos basados en sistemas empotrados, para la asignaturas relacionadas con sistemas de tiempo real. Las herramientas software utilizadas para el desarrollo de los trabajos son el lenguaje de programación Ada’95 y el microkernel de tiempo real MarteOS desarrollado en la Universidad de Cantabria

Control de la ejecución en sistemas de criticidad mixta

[Resumen] En sistemas de tiempo real y, en general, en sistemas críticos, hay una tendencia en alza en utilizar aplicaciones con diferentes niveles de criticidad. Las soluciones basadas en hipervisores son una forma de implementar sistemas de criticidad mixta ya que proporcionan aislamiento temporal y espacial. Sin embargo, la ejecución de una partición puede ser afectada por la ejecución en otros núcleos, lo que se conoce comúnmente como interferencias, poniendo en peligro la ejecución en el tiempo especificado. En este artículo se intenta contribuir dando soluciones realistas a este problema. Se propone una solución de control de la planificación con dos controladores al nivel del hipervisor. Uno de los controladores está orientado a limitar el uso de recursos compartidos a través de la limitación en el uso de los buses en los núcleos no críticos. El otro controlador mide la actividad del núcleo crítico y tomas decisiones sobre la ejecución de los núcleos no críticos.Ministerio de Economía y Competitividad; TIN2014-56158-C4-01/02Generalitat Valenciana; PROMETEOII/2014/03

The Role of Mixed Criticality Technology in Industry 4.0

[EN] Embedded systems used in critical systems, such as aeronautics, have undergone continuous evolution in recent years. In this evolution, many of the functionalities offered by these systems have been adapted through the introduction of network services that achieve high levels of interconnectivity. The high availability of access to communications networks has enabled the development of new applications that introduce control functions with higher levels of intelligence and adaptation. In these applications, it is necessary to manage different components of an application according to their levels of criticality. The concept of "Industry 4.0" has recently emerged to describe high levels of automation and flexibility in production. The digitization and extensive use of information technologies has become the key to industrial systems. Due to their growing importance and social impact, industrial systems have become part of the systems that are considered critical. This evolution of industrial systems forces the appearance of new technical requirements for software architectures that enable the consolidation of multiple applications in common hardware platforms-including those of different criticality levels. These enabling technologies, together with use of reference models and standardization facilitate the effective transition to this approach. This article analyses the structure of Industry 4.0 systems providing a comprehensive review of existing techniques. The levels and mechanisms of interaction between components are analyzed while considering the impact that the handling of multiple levels of criticality has on the architecture itself-and on the functionalities of the support middleware. Finally, this paper outcomes some of the challenges from a technological and research point of view that the authors identify as crucial for the successful development of these technologies.This research was funded by the Spanish Science and Innovation Ministry MICINN: CICYT project PRECON-I4: "Predictable and dependable computer systems for Industry 4.0" TIN201786520-C3-1-R.Simó Ten, JE.; Balbastre, P.; Blanes Noguera, F.; Poza-Lujan, J.; Guasque Ortega, A. (2021). The Role of Mixed Criticality Technology in Industry 4.0. Electronics. 10(3):1-16. https://doi.org/10.3390/electronics1003022611610

Interference-Aware Schedulability Analysis and Task Allocation for Multicore Hard Real-Time Systems

[EN] There has been a trend towards using multicore platforms for real-time embedded systems due to their high computing performance. In the scheduling of a multicore hard real-time system, there are interference delays due to contention of shared hardware resources. The main sources of interference are memory, cache memory, and the shared memory bus. These interferences are a great source of unpredictability and they are not always taken into account. Recent papers have proposed task models and schedulability algorithms to account for this interference delay. The aim of this paper is to provide a schedulability analysis for a task model that incorporates interference delay, for both fixed and dynamic priorities. We assume an implicit deadline task model. We rely on a task model where this interference is integrated in a general way, without depending on a specific type of hardware resource. There are similar approaches, but they consider fixed priorities. An allocation algorithm to minimise this interference (Imin) is also proposed and compared with existing allocators. The results show how Imin has the best rates in terms of percentages of schedulability and increased utilisation. In addition, Imin presents good results in terms of solution times.This work was supported under Grant PLEC2021-007609 funded by MCIN/ AEI/ 10.13039/ 501100011033 and by the "European Union NextGenerationEU/PRTR".Aceituno-Peinado, JM.; Guasque Ortega, A.; Balbastre, P.; Simó Ten, JE.; Crespo, A. (2022). Interference-Aware Schedulability Analysis and Task Allocation for Multicore Hard Real-Time Systems. Electronics. 11(9):1-21. https://doi.org/10.3390/electronics1109131312111