EXTENSIONES AL LENGUAJE ADA Y A LOS SERVICIOS POSIX PARA PLANIFICACIÓN EN SISTEMAS DE TIEMPO REAL ESTRICTO

Esta tesis se ha centrado en el estudio de las políticas basadas en la extracción de holgura y en la asignación dual de prioridades, ambas orientadas a dar servicio a tareas aperiódicas en sistemas real estricto. Estas políticas constituyen una interesante alternativa a las políticas basadas en servidores de carga aperiódicas y han sido ampliamente estudiadas en numerosos trabajos. No obstante, la posibilidad de ser aplicables en la práctica todavía no había sido evaluada en detalle, y éste ha sido el principal objetivo de esta tesis. En este trabajo, ambas políticas son revisadas en profundidad. En el caso de la política basada en la extracción de holgura, algunas de sus principales debilidades han sido corregidas. En particular, se muestra que es posible compartir recursos entre tareas críticas y aperiódicas de una forma sencilla y eficiente, utilizando para ello los mismos protocolos de herencia de prioridad que pueden aplicarse en sistemas en los que sólo existen tareas críticas. La aplicabilidad de estas políticas ha sido valorada incorporándolas en los dos entornos más relevantes hoy en día para la programación de sistemas de tiempo real estricto, el lenguaje de programación Ada y los servicios POSIX. Con este fin se han definido nuevas interfaces para ambas políticas en estos entornos, coherentes con sus principios de diseño y con los servicios que actualmente ofrecen. El diseño de estas interfaces ha supuesto una adaptación de ambas políticas buscando, en todo momento, un equilibrio entre prestaciones y eficiencia. Como parte de este diseño, estas interfaces han sido implementadas en el sistema operativo MaRTE OS. El proceso de implementación ha servido para validar las distintas alternativas qu ehan sido consideradas. Un aspecto importante de una política de planificación en su eficiencia, por lo que este aspecto ha sido evaluado en detalle. Se ha caracterizado de forma analítica el efectoABSTRACT: This thesis is centered on the study of slack stealing and dual priority scheduling policies, both oriented to serve aperiodic tasks in hard real-time systems. These polices, largely studied in previous work, constitute an interesting alternative to policies based on aperiodic servers. However, the possibility of actually being put into practice had not been yet exhaustively evaluated. This has been the main objective of this thesis. Both policies are profoundly revised in this dissertation. In the case of the slack stealing policy, some of its weaknesses have been solved. In particular, this thesis shows that it is possible to share resources between hard and aperiodic tasks in a simple and efficient manner. This can be done by using the same priority inheritance protocols which are used in systems comprising hard tasks only. The applicability of these scheduling policies has been evaluated by means of their incorporation into the two most relevant hard real-time programming environments in use nowadays, the Ada programming language and the POSIX set of services. In order to fulfill this purpose, new interfaces for both policies have been defined in these two environments. These interfaces have been designed in order to be coherent with the environments¿ design principles and the services they currently support. This design has involved the adaptation of the original scheduling policies, trying to optimize the balance between performance and efficiency. As a part of this design, both interfaces have been implemented in the MaRTE OS operating system. These implementations have been useful for validating the different alternatives which have been considered throughout the design process. Since efficiency is an important aspect of any scheduling policy, this aspect has been extremely evaluated in this work. The effect of the implementation of both policies to the task response times has been analytically characterized. This effect has also been quantified, and then the efficiency of both policies has been compared with the fixed-priority preemptive scheduling policy, which is the one normally used in hard real-time systems. The results of this comparative study show that, although the overhead introduced by any VIII ABSTRACT of the two new policies is significant, this overhead lies in a reasonable range. The recently approved POSIX trace services have also been studied in this thesis. The necessity of having some analysis and measurement tools available for the efficiency studies carried out in this thesis led to the incorporation of these services into MaRTE OS. Related to this, a new POSIX/Ada interface for the trace services has also been proposed. In addition, the problem of obtaining temporal metrics of the system from the information of the traces has also been covered.Espinosa Minguet, AR. (2003). EXTENSIONES AL LENGUAJE ADA Y A LOS SERVICIOS POSIX PARA PLANIFICACIÓN EN SISTEMAS DE TIEMPO REAL ESTRICTO [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1774

About Real Time Scheduling Analysis of Ada Applications

International audienc

Real Time Scheduling and its use with Ada

International audienc

Analysis and simulation of scheduling techniques for real-time embedded multi-core architectures

In this modern era of technological progress, multi-core processors have brought significant and consequential improvements in the available processing potential to the world of real-time embedded systems. These improvements impose a rapid increment of software complexity as well as processing demand placed on the underlying hardware. As a consequence, the need for efficient yet predictable multi-core scheduling techniques is on the rise. As part of this thesis, in-depth research of currently available multi-core scheduling techniques, belonging to both partitioned and global approaches, is done in the context of real-time embedded systems. The emphasis is on the degree of their usability on hard real-time systems, focusing on the scheduling techniques offering better processor affinity and the lower number of context switching. Also, an extensive research of currently available real-time test-beds as well as real-time operating systems is performed. Finally, a subset of the analyzed multi-core scheduling techniques comprising PSN-EDF, GSN-EDF, PD$^{2}$ and PD$^{2*}$ is simulated on the real-time test-bed LITMUS$^{RT}$

Une approche intégrée pour la validation et la génération de systèmes critiques par raffinement incrémental de modèles architecturaux

The increasing complexity of distributed realtime and embedded (DRE) systems and their implication in various domains imply new design and development methods. In safety- criticial domains such as space, aeronautical, transport or medicine, their failure could result in the failure of the mission, or in dramatic damages such as human losses. This particular class of systems comes with strong requirements to satisfy safety, reliability and security properties. The Model-driven Engineering (MDE) introduces the concept of «model» - an abstract description of the system and a set of tools (editor, transformation engine, code generator) to simplify and automatize the design, the validation and the implementation of the system. Thus, various abstractions are realized using different domain-specific modeling languages in order to assess one particular aspect of the system and to re-use model-based analysis tools and generative technologies. These various representations may share some commonalities but the consistency between them is hard to validate (for example : Is the analyzed system the same as the generated one ?).This PhD thesis leverages MDE concepts and mechanisms, to enhance the reliability of the model-based development process of DRE systems. Our approach is based on the definition of the architectural and behavioral modeling language AADLHI Ravenscar, a restriction of AADL (Architecture Analysis & Design Language) and its behavioral annex. This subset of AADL constructs, comes up with a semantic close to the one of an imperative programming language, to drive both the analysis and the code generation of the application components and its relying execution platform (middleware) components...L’augmentation de la complexité des systèmes temps-réel répartis embarqués (TR2E) et leur implication dans de nombreux domaines de notre quotidien imposent de nouvelles mé thodes de réalisation. Dans les domaines dits critiques (transport, médecine...) ces systèmes doivent satisfaire des contraintes dures pour garantir leur bon fonctionnement et éviter toutes défaillances qui engendreraient des conséquences financières ou humaines dramatiques. L’Ingénierie Dirigée par les Modèles (IDM) introduit le “modèle” - i.e. une description abstraite du système - et un ensemble d’outils (édition, transformation...) permettant la simplification et l’automatisation des étapes de conception, de validation et de génération du système. Ainsi, différentes abstractions du système sont élaborées dans des formalismes spécifiques de manière à couvrir un aspect du système et à permettre la réutilisation des outils d’analyse et de génération existants. Cependant, ces multiples représentations évoluent à des niveaux d’abstractions différents et il n’est pas toujours évident de mettre en corrélation système analysé et système généré. Ce travail de thèse exploite les concepts et les mécanismes offerts par l’IDM pour améliorer la fiabilité du processus de réalisation des systèmes critiques basé sur les modèles. L’approche que nous avons définie repose sur la définition du langage de modélisation architecturale et comportementale AADL-HI Ravenscar - un sous-ensemble du langage AADL (Architecture Analysis & Design Language) et de son annexe comportementale - contraint pour permettre conjointement l’analyse et la génération de l’ensemble des composants de l’application y compris de son exécutif, avec une sémantique proche d’un langage de programmation impératif..

Actes de l'Ecole d'Eté Temps Réel 2005 - ETR'2005

Pdf des actes disponible à l'URL http://etr05.loria.fr/Le programme de l'Ecole d'été Temps Réel 2005 est construit autour d'exposés de synthèse donnés par des spécialistes du monde industriel et universitaire qui permettront aux participants de l'ETR, et notamment aux doctorants, de se forger une culture scientifique dans le domaine. Cette quatrième édition est centrée autour des grands thèmes d'importance dans la conception des systèmes temps réel : Langages et techniques de description d'architectures, Validation, test et preuve par des approches déterministes et stochastiques, Ordonnancement et systèmes d'exploitation temps réel, Répartition, réseaux temps réel et qualité de service

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI