| 1. |
- Wang, Yang, et al.
(författare)
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Benchmarking OpenMP Programs for Real-Time Scheduling
- 2017
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Ingår i: 2017 IEEE 23Rd International Conference On Embedded And Real-Time Computing Systems And Applications (RTSCA). - : IEEE Computer Society. - 9781538618981
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Konferensbidrag (refereegranskat)abstract
- Real-time systems are shifting from single-core to multi-core processors. Software must be parallelized to fully utilize the computation power of multi-core architecture. OpenMP is a popular parallel programming framework in general and high-performance computing, and recently has drawn a lot of interests in embedded and real-time computing. Much recent work has been done on real-time scheduling of OpenMP-based parallel workload. However, these studies conduct evaluations with randomly generated task systems, which cannot well represent the structure features of OpenMP workload. This paper presents a benchmark suite, ompTGB, to support research on real-time scheduling of OpenMP-based parallel tasks. ompTGB does not only collect realistic OpenMP programs, but also models them into task graphs so that the real-time scheduling researchers can easily understand and use them. We also present a new response time bound for a subset of OpenMP programs and use it to demonstrate the usage of ompTGB.
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| 2. |
- Chen, Gang, et al.
(författare)
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Utilization-Based Scheduling of Flexible Mixed-Criticality Real-Time Tasks
- 2018
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Ingår i: IEEE Transactions on Computers. - : IEEE COMPUTER SOC. - 0018-9340 .- 1557-9956. ; 67:4, s. 543-558
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Tidskriftsartikel (refereegranskat)abstract
- Mixed-criticality models are an emerging paradigm for the design of real-time systems because of their significantly improved resource efficiency. However, formal mixed-criticality models have traditionally been characterized by two impractical assumptions: once any high-criticality task overruns, all low-criticality tasks are suspended and all other high-criticality tasks are assumed to exhibit high-criticality behaviors at the same time. In this paper, we propose a more realistic mixed-criticality model, called the flexible mixed-criticality (FMC) model, in which these two issues are addressed in a combined manner. In this new model, only the overrun task itself is assumed to exhibit high-criticality behavior, while other high-criticality tasks remain in the same mode as before. The guaranteed service levels of low-criticality tasks are gracefully degraded with the overruns of high-criticality tasks. We derive a utilization-based technique to analyze the schedulability of this new mixed-criticality model under EDF-VD scheduling. During run time, the proposed test condition serves an important criterion for dynamic service level tuning, by means of which the maximum available execution budget for low-criticality tasks can be directly determined with minimal overhead while guaranteeing mixed-criticality schedulability. Experiments demonstrate the effectiveness of the FMC scheme compared with state-of-the-art techniques.
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| 3. |
- He, Qingqiang, et al.
(författare)
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On the Consensus Mechanisms of Blockchain/DLT for Internet of Things
- 2018
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Ingår i: 2018 IEEE 13th International Symposium On Industrial Embedded Systems (SIES). - : IEEE. - 9781538641552 ; , s. 150-159
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Konferensbidrag (refereegranskat)abstract
- Internet of Things (IoT) has been experiencing exponential growth in recent years, but still faces many serious challenges. The distributed ledger technology (DLT), e.g., Blockchain, not only appears to be promising to address these technical challenges, but also brings tremendous opportunities for new application and business models. However, the convergence of IoT and DLT is yet a goal far beyond our reach today. Among many problems that have not been sufficiently understood, a fundamental one is how to design appropriate consensus mechanisms for DLT applied to IoT, which is the theme of this paper. We first discuss the potential benefits of applying DLT to IoT, and identify major challenges posed to DLT by IoT. Then we make a survey of existing DLT consensus mechanisms, to summarize major principles and discuss their pros and cons when applied in IoT.
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| 4. |
- He, Qingqiang, et al.
(författare)
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On the degree of parallelism in real-time scheduling of DAG tasks
- 2023
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Ingår i: 2023 Design, Automation & Test in Europe. Conference & Exhibition (DATE). - : IEEE. - 9783981926378 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Real-time scheduling and analysis of parallel tasks modeled as directed acyclic graphs (DAG) have been intensively studied in recent years. The degree of parallelism of DAG tasks is an important characterization in scheduling. This paper revisits the definition and the computing algorithms for the degree of parallelism of DAG tasks, and clarifies some misunderstandings regarding the degree of parallelism which exist in real-time literature. Based on the degree of the parallelism, we propose a real-time scheduling approach for DAG tasks, which is quite simple but rather effective and outperforms the state-of-the-art by a considerable margin.
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| 5. |
- Liang, Haochun, et al.
(författare)
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Response Time Analysis and Optimization of DAG Tasks Exploiting Mutually Exclusive Execution
- 2023
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Ingår i: 2023 60th ACM/IEEE Design Automation Conference (DAC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350323481 - 9798350323498
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Konferensbidrag (refereegranskat)abstract
- There is an increasing move towards implementing embedded real-time systems upon multiprocessors with parallel applications, which are usually modeled as Directed Acyclic Graphs (DAGs). Plentiful work has been presented to optimize the bound of Worst-Case Response Time (WCRT) since the cornerstone work proposed by Graham in 1969. However, all these works are developed on the basis of Graham's bound and failed to tackle the root of pessimism in it. In this work, we present a novel method to optimize the WCRT bound of a DAG task by designing mutually exclusive groups so that a sequential execution is enforced for some nodes, under which the problem of bounding WCRT becomes a problem of identifying a mutually exclusive path and thus does not suffer the pessimism in Graham's bound. Experiments are conducted to evaluate the performance of our method against other WCRT optimization approaches in the state-of-the-art.
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| 6. |
- Sun, Jinghao, et al.
(författare)
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Real-Time Scheduling and Analysis of OpenMP Task Systems with Tied Tasks
- 2017
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Ingår i: 2017 IEEE Real-Time Systems Symposium (RTSS). - : IEEE. - 9781538614143 ; , s. 92-103
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Konferensbidrag (refereegranskat)abstract
- OpenMP is a promising framework for developing parallel real-time software on multi-cores. Although similar to the DAG task model, OpenMP task systems are significantly more difficult to analyze due to constraints posed by the OpenMP specification. An important feature in OpenMP is tied tasks, which must execute on the same thread during the whole life cycle. Although tied tasks enjoy benefits in simplicity and efficiency, it was considered to be not suitable to real-time systems due to its complex behavior. In this paper, we study the real-time scheduling and analysis of OpenMP task systems with tied tasks. First, we show that under the existing scheduling algorithms in OpenMP, tied tasks indeed may lead to extremely bad timing behaviors where the parallel workload is sequentially executed completely. To solve this problem, we proposed a new scheduling algorithm and developed two response time bounds for it, with different trade-off between simplicity and analysis precision. Experiments with both randomly generated OpenMP task systems and realistic OpenMP programs show that the response time bounds obtained by our approach for tied task systems are very close to that of untied tasks.
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