| 61. |
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| 62. |
- Kraft, Johan, et al.
(författare)
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Continuous Constant-Memory Monitoring of Embedded Software Timing
- 2011
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Ingår i: 2nd International Workshop on Analysis Tools and Methodologies for Embedded and Real-time Systems (WATERS'11), satellite workshop of EUROMICRO Conference on Real-Time Systems (ECRTS'11).
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Konferensbidrag (refereegranskat)abstract
- A method is presented for generating statistical models of timing data continuously over very long monitoring sessions. This method is intended for memory-efficient runtime modeling of timing properties in embedded software systems, such as execution times or inter-arrival times, but is a quite generic method that should be applicable for other purposes and domains as well. Specifically, we intend to use this method as a component in automatic generation of simulation models for probabilistic timing analysis of complex embedded software systems. Given a stream of data as input, this method gradually builds up a statistical model capturing the approximate distribution of the data. The method uses a modest and fixed amount of on-target RAM, decided by the desired accuracy of the model, and allows for long monitoring sessions covering billions of data points. The paper presents the motivation, algorithm, a prototype implementation and evaluation using real execution time data from an ARM7 microcontroller.
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| 63. |
- Kraft, Johan, et al.
(författare)
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Software Maintenance Research in the PROGRESS Project for Predictable Embedded Software Systems
- 2011
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Ingår i: 15th European Conference on Software Maintenance and Reengineering (CSMR'11). - Los Alamitos : IEEE Computer Society. - 9780769543437 ; , s. 335-338
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Konferensbidrag (refereegranskat)abstract
- PROGRESS is a project and strategic research centre at Malardalen University in Sweden that is funded for 2006-2010 by the Swedish Foundation for Strategic Research (SSF). PROGRESS research targets embedded software in the vehicular, automation, and telecom domains, focusing on the areas of component technology, verification and analysis for predictability, predictable execution, as well as reuse and maintenance of legacy embedded software. We first describe the funding, organization and research areas of PROGRESS, and then give several examples of PROGRESS research that addresses maintenance of legacy embedded software with the goal to improve program comprehension, quality assurance, and debugging. Specifically, we describe research in tracing and trace visualization, impact analysis of temporal behavior, slicing, and system-specific static analyses.
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| 64. |
- Lindgren, M., et al.
(författare)
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Applicability of using internal GPGPUs in industrial control systems
- 2014
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Ingår i: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014. - 9781479948468 ; , s. Article number 7005096-
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Konferensbidrag (refereegranskat)abstract
- Industrial control systems are continuously increasing in functionality, connectivity, and levels of integration, and as a consequence they require more computational power. At the same time, these systems have specific requirements related to cost, reliability, timeliness, and thermal power dissipation, which put restrictions on the hardware and software used. Today the high-end embedded CPUs not only provide multiple cores, but also integrated graphics processors (GPU) at close to no additional cost. The use of GPUs for general processing have several potential values in industrial control systems; 1) the added computational power and the high parallelism could pave way for new functionality and 2) the integrated GPU could potentially replace other hardware and thereby reduce the overall cost. In this paper we investigate the applicability of using integrated GPUs in industrial control systems. We do this by evaluating the performance of GPUs with respect to computational problem types and sizes typically found in industrial control systems. In the end we conclude that GPUs are no obvious match for industrial control systems and that several hurdles remain before a wide adoption can be motivated.
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| 65. |
- Liu, Meng, et al.
(författare)
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A Server-based Approach for Overrun Management in Multi-Core Real-Time Systems
- 2014
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Konferensbidrag (refereegranskat)abstract
- This paper presents a server-based framework for task overrun management in multi-core real-time systems. Unlike most existing scheduling methods which usually assume a single upper bound of the Worst-Case Execution Time (WCET) for each task, our approach targets scenarios with task overruns. The main idea of our framework is to employ Synchronized Deferrable Servers (SDS) to deal with globally scheduled task overruns, while a partitioned scheduling approach is applied on regular task executions. Moreover, we provide a deterministic Worst- Case Response Time (WCRT) analysis focusing on hard timing constraints, along with a probabilistic analysis of Deadline Miss Ratio (DMR) for soft real-time applications. In the evaluation phase, we have implemented two types of experiments evaluating different timing constraints.
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| 66. |
- Liu, Meng, et al.
(författare)
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An Adaptive Server-Based Scheduling Framework with Capacity Reclaiming and Borrowing
- 2014
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Ingår i: RTCSA 2014 - 20th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications. - 9781479939534 ; , s. Article number 6910548-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present a new reservation based scheduling framework for soft real-time systems using EDF algorithm (called CARB-EDF). This framework has the features of Capacity Adaptation, Reclaiming and Borrowing. This framework can simplify the initial configuration of the system, where the system designer does not need to provide any estimations of task execution times. We also present a Chebyshev’s inequality based predictor to estimate task execution times. A number of simulation-based experiments have been implemented. According to the results compared with some related works, our scheduling framework can provide a better performance with acceptable extra scheduling overhead.
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| 67. |
- Liu, Meng, et al.
(författare)
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An EVT-based Worst-Case Response Time Analysis of Complex Real-Time Systems
- 2013
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Ingår i: Proceedings of the 8th IEEE International Symposium on Industrial Embedded Systems, SIES 2013. - 9781479906581 ; , s. 249-258
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Konferensbidrag (refereegranskat)abstract
- In recent years, the complexity of real-time embedded systems has increased dramatically. For those modern real-time systems, the limitations of original static Response Time Analysis (RTA) become more and more conspicuous. Most static analysis methods not only require much detailed system information, but also only target to some specific system model with non-realistic assumptions. As a result, those methods may produce overly pessimistic results, making them unsuitable to be applied on a complex industrial system. The best system model may be the system itself. Therefore, statistical RTA, which can produce probabilistic analysis results based on samples provided by real systems or simulators, may become more expedient. Statistical RTA usually requires more relaxed assumptions and less system information than static RTA. In this paper, we present an Extreme Value Theory (EVT) based method to compute Worst-Case Response Time (WCRT) targeting complex real-time systems. In the evaluation phase, we have applied this method to the calculation of worst-case transmission delays of messages over Controller Area Network (CAN), and some comparisons with static RTA are also provided. According to the experimental results, as the system complexity increases, our approach performs much more stable and less pessimistic.
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| 68. |
- Liu, Meng, et al.
(författare)
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Applying the Peak Over Thresholds Method on Worst-Case Response Time Analysis of Complex Real-Time Systems
- 2013
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Ingår i: 2013 IEEE 19th International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2013. - 9781479908509 ; , s. 22-31
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Konferensbidrag (refereegranskat)abstract
- The predictability of timing behavior is a very important performance issue of a real-time system. As the complexity of modern industrial systems increases, analyzing the timing behaviors of those systems becomes more and more challenging. Most of the existing analysis methods depend on static and detailed information of the systems under analysis. However, sometimes only partial information of a system can be available, or it may require too much effort on obtaining those details, making those analysis methods much less feasible. Moreover, those methods usually focus on some specific system models with unrealistic assumptions, consequently, applying those methods on a complex industrial real-time system may result in overly pessimistic results. Therefore, in this paper, we propose a statistical method to compute Worst-Case Response Times (WCRTs) of complex real-time systems regarding soft timing constraints, which can provide a higher general applicability with less required system information. Our approach employs a Peak Over Thresholds (POT) method, which is a branch of the Extreme Value Theory (EVT). For the evaluation, we have applied this approach on the analysis of message transmission latencies over Controller Area Networks (CAN).
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| 69. |
- Liu, Meng
(författare)
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On Improving Resource Utilization in Distributed Real-Time Embedded Systems
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In our modern life, embedded systems are playing an essential role. An embedded system is a computer system embedded into a certain device, in order to achieve computing functions. Beyond all doubt, as a validated system, the functional correctness must be guaranteed. However, for many embedded systems, timeliness also plays an important role in addition to the correctness of the functionalities. For example, in an automotive braking system, the braking function needs to be processed within a limited time duration in order to avoid accidents. Such systems are known as real-time embedded systems.In these systems, there can be plenty of software programs (called tasks) sharing limited computing resources (e.g. processors, memories). If the system executes tasks in a random way, the whole system will become unpredictable. As a result, the system designers will not be able to verify if the system design can fulfill all the timing requirements or not. In other words, the system is not guaranteed to be safe. Therefore, system designers need to carefully implement algorithms to schedule all the tasks in a predictable manner. Regarding each scheduling algorithm, schedulability analyses are proposed which are used to check if the requirements can be satisfied.Unfortunately, many real-time systems reserve too much computing resource for the sake of fulfilling timing requirements, without taking into account resource utilization. As a result, system resources cannot be efficiently utilized, which can cause significant resource waste in reality. Therefore, in this thesis, we aim to improve resource utilization in modern distributed real-time embedded systems. We try to tackle this problem from the following two aspects.Investigating tighter timing analyses. Due to the difficulty in performing precise mathematical schedulability analyses, most of the existing analyses include varying degrees of pessimism. In other words, the actual performance of the system can be much better than the predictions. If we can reduce the pessimism in schedulability analyses, we can then admit more workload into the system.Proposing new scheduling frameworks. It is difficult to find a scheduling algorithm which is suitable for all the situations. Therefore, we need different mechanisms to handle specific system characteristics in order to improve the resource utilization.
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| 70. |
- Liu, Meng, et al.
(författare)
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Response time analysis for static priority based SpaceWire networks
- 2012
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Ingår i: Proceeings of the 2nd International Workshop on Worst-Case Traversal Time (WCTT '12). - New York, NY, USA : ACM. - 9781450316866 ; , s. 7-14
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Konferensbidrag (refereegranskat)abstract
- The SpaceWire network standard is used in spacecraft communications and has been selected for future ESA satellites. In order to guarantee the safety and reliability of on-board systems, the designers have to make sure that all critical timing constraints are satisfied. The SpaceWire network is a wormhole based network which makes its timing analysis significantly complex. Some methods for computing upper-bounds of end-to-end delays of certain wormhole network models have been developed. However, those models require some explicit assumptions and dedicated real-time mechanisms which cannot be supported by the current SpaceWire networks. Moreover, some work has proposed analysis approaches for SpaceWire networks assuming the Round-Robin arbitration scheme only. In this paper, we focus on the priority based arbitration scheme instead and we propose a worst-case response time analysis to evaluate the end-to-end delays of traffic transmissions in SpaceWire networks. The corresponding proofs to our analysis are presented along with a case study. © 2012 ACM.
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