A Survey of Research into Mixed Criticality Systems

This survey covers research into mixed criticality systems that has been published since Vestal’s seminal paper in 2007, up until the end of 2016. The survey is organised along the lines of the major research areas within this topic. These include single processor analysis (including fixed priority and EDF scheduling, shared resources and static and synchronous scheduling), multiprocessor analysis, realistic models, and systems issues. The survey also explores the relationship between research into mixed criticality systems and other topics such as hard and soft time constraints, fault tolerant scheduling, hierarchical scheduling, cyber physical systems, probabilistic real-time systems, and industrial safety standards

The Family of MapReduce and Large Scale Data Processing Systems

In the last two decades, the continuous increase of computational power has produced an overwhelming flow of data which has called for a paradigm shift in the computing architecture and large scale data processing mechanisms. MapReduce is a simple and powerful programming model that enables easy development of scalable parallel applications to process vast amounts of data on large clusters of commodity machines. It isolates the application from the details of running a distributed program such as issues on data distribution, scheduling and fault tolerance. However, the original implementation of the MapReduce framework had some limitations that have been tackled by many research efforts in several followup works after its introduction. This article provides a comprehensive survey for a family of approaches and mechanisms of large scale data processing mechanisms that have been implemented based on the original idea of the MapReduce framework and are currently gaining a lot of momentum in both research and industrial communities. We also cover a set of introduced systems that have been implemented to provide declarative programming interfaces on top of the MapReduce framework. In addition, we review several large scale data processing systems that resemble some of the ideas of the MapReduce framework for different purposes and application scenarios. Finally, we discuss some of the future research directions for implementing the next generation of MapReduce-like solutions.Comment: arXiv admin note: text overlap with arXiv:1105.4252 by other author

A survey of techniques for reducing interference in real-time applications on multicore platforms

This survey reviews the scientific literature on techniques for reducing interference in real-time multicore systems, focusing on the approaches proposed between 2015 and 2020. It also presents proposals that use interference reduction techniques without considering the predictability issue. The survey highlights interference sources and categorizes proposals from the perspective of the shared resource. It covers techniques for reducing contentions in main memory, cache memory, a memory bus, and the integration of interference effects into schedulability analysis. Every section contains an overview of each proposal and an assessment of its advantages and disadvantages.This work was supported in part by the Comunidad de Madrid Government "Nuevas Técnicas de Desarrollo de Software de Tiempo Real Embarcado Para Plataformas. MPSoC de Próxima Generación" under Grant IND2019/TIC-17261

Design and implementation of a modular scheduling simulator for aerospace applications

Tese de mestrado em Engenharia Informática, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2012Sistemas tempo-real têm de produzir os resultados esperados de cada tarefa atempadamente de acordo com a urgência de cada uma. Desde os anos 70 tentam-se obter formas de coordenar a execução das tarefas para cumprir todos os prazos através de algoritmos de escalonamento. Na sua maioria estes algoritmos apesar de terem requerido um extensivo trabalho por parte de quem os criou são simples de compreender. Um dos mais antigos é o algoritmo “Earliest Deadline First”, que consiste em dar maior prioridade às tarefas mais urgentes. Alguns sistemas devido às suas características particulares obedecem a modelos mais complexos. É o caso dos sistemas aeronáuticos onde é necessário manter o isolamento entre as funcionalidades. As funções são agrupadas logicamente em contentores denominados partições. Para garantir essa separação no domínio do tempo introduz-se um esquema de escalonamento a dois níveis. Um primeiro que determina as janelas temporais a dar a cada partição e um segundo nível onde estão as partições e respectivas funções. Os algoritmos de escalonamento utilizados em cada nível não tem de ser iguais; no segundo nível, cada partição pode usar um algoritmo diferente. Após estudar o que actualmente existe decidimos orientar o nosso trabalho para partições e escalonamento hierárquico pois é de onde poderemos vir a obter melhores resultados e soluções para sistemas futuros. Fazendo uso de padrões de desenho, bem como características do Java, tais como herança e polimorfismo conseguimos obter uma solução que após implementada permite aos seus utilizadores simularem a execução de um sistema que estes definam. Permite também obter os eventos e com estes mostrar ao utilizador o que o simulador fez em cada momento do sistema podendo estes resultados ser exibidos em formato textual ou fazer uso de outras aplicações de visualização de resultados.Real-time systems are required to produce results from each task in time, according to the urgency of each one. Since the 1970s researchers try to obtain ways to coordinate the execution of tasks to meet all deadline, by using scheduling algorithms. Although the majority of these algorithms required an extensive work from those who created them, they are simple to understand. One of the oldest is the Earliest Deadline First algorithm, which attributes higher priority to the most urgent tasks. Due to their characteristics, some systems obey to more complex models; this is the case of aerospace systems. These systems require full isolation between functionalities. The functions, composed of tasks (processes), are logically grouped into partitions. To ensure separation in the time domain, a two level scheduling scheme is introduced. The first level determinates the time windows to assign to each partition; in the second level, tasks in each partition compete among them for the execution time assigned to the latter. The scheduling algorithms used in each level do not need to be the same; in the second level, each partition may even employ a different algorithm to schedule its tasks. After studying what currently exists we have decided to guide our work to partitions and hierarchical scheduling because it is where we see producing better results and solutions for future systems. Using design patterns as well as Java properties such as inheritance and polymorphism we were able to obtain a solution that after implemented allows users to simulate the execution of a system defined by them. The tool allows obtaining events and showing them to the user and giving feedback, these events represent the basic functionalities of a real-time system, such as, job launch and job deadline miss and others. These results can be shown in textual form or use other applications of results visualization