Percorrer por autor "Pinho, Luís Miguel"
A mostrar 1 - 10 de 122
Resultados por página
Opções de ordenação
- Abstract Timers and their Implementation onto the ARM Cor tex-M family of MCUsPublication . Lindgren, Per; Fresk, Emil; Lindner, Marcus; Lindner, Andreas; Pereira, David; Pinho, Luís MiguelReal-Time For the Masses (RTFM) is a set of languages andto ols b eing develop ed to facilitate emb edded software development and provide highly efficient implementations gearedto static verification. The RTFM-kernel is an architecturedesigned to provide highly efficient and predicable Stack Resource Policy based scheduling, targeting bare metal (singlecore) platforms.We contribute b eyond prior work by intro ducing a platform independent timer abstraction that relies on existingRTFM-kernel primitives. We develop two alternative implementations for the ARM Cortex-M family of MCUs: ageneric implementation, using the ARM defined SysTick-/DWT hardware; and a target sp ecific implementation, using the match compare/free running timers. While sacrificing generality, the latter is more flexible and may reduceoverall overhead. Invariants for correctness are presented,and metho ds to static and run-time verification are discussed. Overhead is b ound and characterized. In b oth casesthe critical section from release time to dispatch is less than2us on a 100MHz MCU. Queue and timer mechanisms aredirectly implemented in the RTFM-core language and canb e included in system-wide scheduling analysis.
- Adaptive offloading for infotainment systemsPublication . Ferreira, Luís Lino; Pinho, Luís Miguel; Albano, Michele; Teixeira, CésarInfotainment applications in vehicles are currently supported both by the in-vehicle platform, as well as by user’s smart devices, such as smartphones and tablets. More and more the user expects that there is a continuous service of applications inside or outside of the vehicle, provided in any of these devices (a simple but common example is hands-free mobile phone calls provided by the vehicle platform). With the increasing complexity of ‘apps’, it is necessary to support increasing levels of Quality of Service (QoS), with varying resource requirements. Users may want to start listening to music in the smartphone, or video in the tablet, being this application transparently ‘moved’ into the vehicle when it is started. This paper presents an adaptable offloading mechanism, following a service-oriented architecture pattern, which takes into account the QoS requirements of the applications being executed when making decisions.
- Allocation of Parallel Real-Time Tasks in Distributed Multi-core Architectures supported by an FTT-SE NetworkPublication . Martínez, Ricardo Garibay; Nelissen, Geoffrey; Ferreira, Luís Lino; Pinho, Luís MiguelDistributed real-time systems such as automotive applications are becoming larger and more complex, thus, requiring the use of more powerful hardware and software architectures. Furthermore, those distributed applications commonly have stringent real-time constraints. This implies that such applications would gain in flexibility if they were parallelized and distributed over the system. In this paper, we consider the problem of allocating fixed-priority fork-join Parallel/Distributed real-time tasks onto distributed multi-core nodes connected through a Flexible Time Triggered Switched Ethernet network. We analyze the system requirements and present a set of formulations based on a constraint programming approach. Constraint programming allows us to express the relations between variables in the form of constraints. Our approach is guaranteed to find a feasible solution, if one exists, in contrast to other approaches based on heuristics. Furthermore, approaches based on constraint programming have shown to obtain solutions for these type of formulations in reasonable time.
- An Ada framework for QoS-Aware applicationsPublication . Pinho, Luís Miguel; Nogueira, Luís; Barbosa, RicardoIn this paper we present a framework for managing QoS-aware applications in a dynamic, ad-hoc, distributed environment. This framework considers an available set of wireless/mobile and fixed nodes, which may temporally form groups in order to process a set of related services, and where there is the need to support different levels of service and different combinations of quality requirements. This framework is being developed both for testing and validating an approach, based on multidimensional QoS properties, which provides service negotiation and proposal evaluation algorithms, and for assessing the suitability of the Ada language to be used in the context of dynamic, QoS-aware systems.
- An architecture for reliable distributed computer-controlled systemsPublication . Pinho, Luís Miguel; Vasques, FranciscoIn Distributed Computer-Controlled Systems (DCCS), both real-time and reliability requirements are of major concern. Architectures for DCCS must be designed considering the integration of processing nodes and the underlying communication infrastructure. Such integration must be provided by appropriate software support services. In this paper, an architecture for DCCS is presented, its structure is outlined, and the services provided by the support software are presented. These are considered in order to guarantee the real-time and reliability requirements placed by current and future systems.
- An Execution Model for Fine-Grained Parallelism in AdaPublication . Pinho, Luís Miguel; Moore, Brad; Michell, Stephen; Taft, S. TuckerThis paper extends the authors earlier proposal for providing Ada with support for fine-grained parallelism with an execution model based on the concept of abstract executors, detailing the progress guarantees that these executors must provide and how these can be assured even in the presence of potentially blocking operations. The paper also describes how this execution model can be applied to real-time systems.
- Analysis of self-interference within DAG tasksPublication . Fonseca, José; Nélis, Vincent; Nelissen, Geoffrey; Pinho, Luís MiguelNo abstract (2-pages paper) Few years ago, the frontier separating the real-time embedded domain from the high-performance computing domain was neat and clearly defined. Nowadays, many contemporary applications no longer find their place in either category as they manifest both strict timing constraints and work-intensive computational demands. The only way forward to cope with such orthogonal requirements is to embrace the parallel execution programming paradigm on the emergent scalable and energy-efficient multicore/many-core architectures
- Building adaptable, QoS-aware dependable embedded systemsPublication . Nogueira, Luís; Pinho, Luís MiguelMost of today’s embedded systems are required to work in dynamic environments, where the characteristics of the computational load cannot always be predicted in advance. Furthermore, resource needs are usually data dependent and vary over time. Resource constrained devices may need to cooperate with neighbour nodes in order to fulfil those requirements and handle stringent non-functional constraints. This paper describes a framework that facilitates the distribution of resource intensive services across a community of nodes, forming temporary coalitions for a cooperative QoSaware execution. The increasing need to tailor provided service to each application’s specific needs determines the dynamic selection of peers to form such a coalition. The system is able to react to load variations, degrading its performance in a controlled fashion if needed. Isolation between different services is achieved by guaranteeing a minimal service quality to accepted services and by an efficient overload control that considers the challenges and opportunities of dynamic distributed embedded systems.
- Capacity sharing and stealing in dynamic server-based real-time systemsPublication . Nogueira, Luís; Pinho, Luís MiguelThis paper proposes a dynamic scheduler that supports the coexistence of guaranteed and non-guaranteed bandwidth servers to efficiently handle soft-tasks’ overloads by making additional capacity available from two sources: (i) residual capacity allocated but unused when jobs complete in less than their budgeted execution time; (ii) stealing capacity from inactive non-isolated servers used to schedule best-effort jobs. The effectiveness of the proposed approach in reducing the mean tardiness of periodic jobs is demonstrated through extensive simulations. The achieved results become even more significant when tasks’ computation times have a large variance.
- Capacity sharing and stealing in serverbased real-time systemsPublication . Nogueira, Luís; Pinho, Luís MiguelA dynamic scheduler that supports the coexistence of guaranteed and non-guaranteed bandwidth servers is proposed. Overloads are handled by an efficient reclaiming of residual capacities originated by early completions as well as by allowing reserved capacity stealing of non-guaranteed bandwidth servers. The proposed dynamic budget accounting mechanism ensures that at a particular time the currently executing server is using a residual capacity, its own capacity or is stealing some reserved capacity, eliminating the need of additional server states or unbounded queues. The server to which the budget accounting is going to be performed is dynamically determined at the time instant when a capacity is needed. This paper describes and evaluates the proposed scheduling algorithm, showing that it can efficiently reduce the mean tardiness of periodic jobs. The achieved results become even more significant when tasks’ computation times have a large variance.