Modelagem de relações entre tarefas usando interfaces gráficas aplicada em sistemas de tempo-real
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Data
2019-08-16
Autores
Peronaglio, Fernanda Fernandes
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A análise de sistemas computacionais por meio de simulação depende fortemente de como as tarefas a serem executadas serão modeladas. Isso é ainda mais importante quando se fala de sistemas de tempo-real, em que tarefas devem ser atendidas dentro dos intervalos corretos e a análise por simulação evita perigos possivelmente presentes se executadas no ambiente real. Entretanto, simuladores de tarefas tipicamente as modelam como blocos independentes de carga de trabalho. Embora isso seja correto ou aceitável em muitas situações, isso não é sempre verdade em sistemas de tempo-real, pois normalmente aplicações desse tipo apresentam relações de dependência entre si. Em alguns simuladores isso é resolvido com a escrita do modelo de tarefa em alguma linguagem de modelagem específica, o que evidentemente dificulta o trabalho de simulação se comparado com abordagens gráficas. Desse modo, aqui se propõe uma abordagem que permita a modelagem de interações entre tarefas, em especial de tempo-real, por meio de interfaces visuais, sem comprometer a corretude do motor de simulação. A modelagem visual permite que o usuário se concentre no problema a ser avaliado e não na programação de seus detalhes, melhorando a eficiência desse processo. Na abordagem proposta se parte do conceito de árvores hierárquicas para estabelecer associações entre tarefas, elementos de processamento e recursos do sistema. As relações previstas entre tarefas incluem precedência, sincronismo, paralelismo e exclusão mútua. A validação dessa abordagem ocorre com sua aplicação no simulador de algoritmos de escalonamento RTsim, que já apresenta características interessantes de simulação, como interfaces para modelagem de escalonadores e de auxílio ao ensino. Assim como outros simuladores, o RTsim originariamente trata tarefas como blocos independentes de carga de trabalho, o que facilita a verificação dos efeitos desta abordagem na modelagem. Os resultados obtidos mostram que os procedimentos de modelagem de relações entre tarefas, na forma como definidos aqui, são aplicáveis em simuladores de eventos discretos, conforme avaliações de sua correção e usabilidade.
Analysis of computing systems through simulation is strongly dependent of how tasks to be executed are modeled. This is even more important in real-time systems, where tasks must be executed before their deadlines, and their simulation avoid possible risks present in the real environment. However, simulators of such tasks usually model them as independent load blocks. Although this is correct for many systems, it is not always true for real-time systems, where applications usually have dependence relationships between tasks. In some simulators this is solved by enforcing the user to write the model in some modeling or simulation language, clearly making the simulation harder when compared to graphical approaches. Therefore, a graphical approach for task modeling is proposed. This approach is specially aimed to real-time tasks and does not compromise simulation accuracy. Graphical, that is visual, modeling allows for the user to focus on the problem to be evaluated and not in programming details of the system, improving the efficiency of this process. This proposal is based on the hierarchical tree concept to establish associations between tasks, processing elements and system resources. Chosen relationships include precedence, synchronism, parallelism and mutual exclusion. This proposal is validated through its application in a simulator of real-time scheduling algorithms named RTsim, which already offers interesting modeling/simulation characteristics such as interfaces to model schedulers and to teaching. RTsim, as others simulators do, models its tasks as independent blocks, what facilitates the verification of this approach effects to modeling. The results achieved with the tests show that procedures for modeling relationships between tasks, as defined in this dissertation, are applicable to discrete event simulators, according to the evaluations of this correctness and usability.
Analysis of computing systems through simulation is strongly dependent of how tasks to be executed are modeled. This is even more important in real-time systems, where tasks must be executed before their deadlines, and their simulation avoid possible risks present in the real environment. However, simulators of such tasks usually model them as independent load blocks. Although this is correct for many systems, it is not always true for real-time systems, where applications usually have dependence relationships between tasks. In some simulators this is solved by enforcing the user to write the model in some modeling or simulation language, clearly making the simulation harder when compared to graphical approaches. Therefore, a graphical approach for task modeling is proposed. This approach is specially aimed to real-time tasks and does not compromise simulation accuracy. Graphical, that is visual, modeling allows for the user to focus on the problem to be evaluated and not in programming details of the system, improving the efficiency of this process. This proposal is based on the hierarchical tree concept to establish associations between tasks, processing elements and system resources. Chosen relationships include precedence, synchronism, parallelism and mutual exclusion. This proposal is validated through its application in a simulator of real-time scheduling algorithms named RTsim, which already offers interesting modeling/simulation characteristics such as interfaces to model schedulers and to teaching. RTsim, as others simulators do, models its tasks as independent blocks, what facilitates the verification of this approach effects to modeling. The results achieved with the tests show that procedures for modeling relationships between tasks, as defined in this dissertation, are applicable to discrete event simulators, according to the evaluations of this correctness and usability.
Descrição
Palavras-chave
Modelagem, Escalonamento, Sistemas de tempo-real, Modeling, Scheduling, Real-time system