@article { abs-2104.06366,
  author = {Shi, Junjie and Duy Thien Pham, Jan and M\"unch, Malte and Viktor Hafemeister, Jan and Chen, Jian-Jia and Chen, Kuan-Hsun},
  title = {Supporting Multiprocessor Resource Synchronization Protocols in RTEMS},
  journal = {CoRR},
  year = {2021},
  volume = {abs/2104.06366},
  url = {https://arxiv.org/abs/2104.06366},
  keywords = {kuan},
  confidential = {n},
  abstract = {When considering recurrent tasks in real-time systems, concurrent accesses to shared resources, can cause race conditions or data corruptions. Such a problem has been extensively studied since the 1990s, and numerous resource synchronization protocols have been developed for both uni-processor and multiprocessor real-time systems, with the assumption that the implementation overheads are negligible. However, in practice, the implementation overheads may impact the performance of different protocols depending upon the practiced scenarios, e.g., resources are accessed locally or remotely, and tasks spin or suspend themselves when the requested resources are not available. In this paper, to show the applicability of different protocols in real-world systems, we detail the implementation of several state-of-the-art multiprocessor resource synchronization protocols in RTEMS. To study the impact of the implementation overheads, we deploy these implemented protocols on a real platform with synthetic task set. The measured results illustrate that the developed resource synchronization protocols in RTEMS are comparable to the existed protocol, i.e., MrsP.},
}

@inproceedings { GECCO-Richter-etal2010,
  author = {Richter, Jakob and Shi, Junjie and Chen, Jian-Jia and Rahnenf\"uhrer, J\"org and Lang, Michel},
  title = {Model-based Optimization with Concept Drifts},
  booktitle = {The Genetic and Evolutionary Computation Conference},
  year = {2020},
  address = {accepted and to appear},
  confidential = {n},
}

@inproceedings { DBLP:conf/gecco/RichterSCRL20,
  author = {Richter, Jakob and Shi, Junjie and Chen, Jian-Jia and Rahnenf\"uhrer, J\"org and Lang, Michel},
  title = {Model-based optimization with concept drifts},
  booktitle = {GECCO},
  year = {2020},
  pages = {877--885},
  publisher = {ACM},
  confidential = {n},
}

@inproceedings { DBLP:conf/rtas/ShiUBC19,
  author = {Shi, Junjie and Ueter, Niklas and Br\"uggen, Georg von der and Chen, Jian-Jia},
  title = {Multiprocessor Synchronization of Periodic Real-Time Tasks Using Dependency Graphs},
  booktitle = {25th IEEE Real-Time and Embedded Technology and Applications Symposium, RTAS},
  year = {2019},
  pages = {279--292},
  url = {https://doi.org/10.1109/RTAS.2019.00031},
  keywords = {georg, junjie},
  file = {https://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2019-rtas-junjie.pdf},
  confidential = {n},
  abstract = {When considering recurrent real-time tasks in multiprocessor systems, access to shared resources, via so-called critical sections, can jeopardize the schedulability of the system. The reason is that resource access is mutual exclusive and a task must finish its execution of the critical section before another task can access the same resource. Therefore, the problem of multiprocessor synchronization has been extensively studied since the 1990s, and a large number of multiprocessor resource sharing protocols have been developed and analyzed. Most protocols assume work-conserving scheduling algorithms which make it impossible to schedule task sets where a critical section of one task is longer than the relative deadline of another task that accesses the same resource. The only known exception to the work-conserving paradigm is the recently presented Dependency Graph Approach where the order in which tasks access a shared resource is not determined online, but based on a pre-computed dependency graph. Since the initial work only considers frame-based task systems, this paper extends the Dependency Graph Approach to periodic task systems. We point out the connection to the uniprocessor non-preemptive scheduling problem and exploit the related algorithms to construct dependency graphs for each resource. To schedule the derived dependency graphs, List scheduling is combined with an earliest-deadline-first heuristic. We evaluated the performance considering synthesized task sets under different configurations, where a significant improvement of the acceptance ratio compared to other resource sharing protocols is observed. Furthermore, to show the applicability in real-world systems, we detail the implementation in LITMUS RT and report the resulting scheduling overheads.},
}

@inproceedings { DBLP:conf/rtcsa/ShiUBC19,
  author = {Shi, Junjie and Ueter, Niklas and Br\"uggen, Georg von der and Chen, Jian-Jia},
  title = {Partitioned Scheduling for Dependency Graphs in Multiprocessor Real-Time Systems},
  booktitle = {25th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA},
  year = {2019},
  pages = {1--12},
  address = {Hangzhou, China},
  month = {August 18-21},
  url = {https://ieeexplore.ieee.org/document/8864591},
  keywords = {georg, junjie},
  file = {https://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/shi-partitioned.pdf},
  confidential = {n},
  abstract = {Effectively handling precedence constraints and resource synchronization is a challenging problem in the era of multiprocessor systems even with massively parallel computation power. One common approach is to apply list scheduling to a given task graph with precedence constraints. However, in some application scenarios, such as the OpenMP task model and multiprocessor partitioned scheduling for resource synchronization using binary semaphores, several operations can be forced to be tied to the same processor, which invalidates the list scheduling. This paper studies a special case of this challenging scheduling problem, where a task comprised of (at most) three subtasks is executed sequentially on the same processor and the second subtasks of the tasks may have sequential dependencies, e.g., due to synchronization. We demonstrate the limits of existing algorithms and provide effective heuristics considering preemptive execution. The evaluation results show a significant improvement, compared to the existing multiprocessor partitioned scheduling strategies.},
}

@inproceedings { dong2018rtas,
  author = {Dong, Zheng and Liu, Cong and Bateni, Soroush and Chen, Kuan-Hsun and Chen, Jian-Jia and Br\"uggen, Georg von der and Shi, Junjie},
  title = {Shared-Resource-Centric Limited Preemptive Scheduling: A Comprehensive Study of Suspension-based Partitioning Approaches},
  booktitle = {IEEE Real-Time and Embedded Technology and Applications Symposium RTAS},
  year = {2018},
  address = {Porto, Portugal},
  month = {April 11-13},
  url = {https://ieeexplore.ieee.org/document/8430080},
  keywords = {kuan, georg, junjie},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2018_rtas_zheng.pdf},
  confidential = {n},
  abstract = {This paper studies the problem of scheduling a set of hard real-time sporadic tasks that may access CPU cores and
a shared resource. Motivated by the observation that the CPU resource is often abundant compared to the shared resources in multi-core and many-core systems, we propose to resolve this problem from a counter-intuitive shared-resource-centric perspective, focusing on judiciously prioritizing and scheduling tasks’ requests in a limited preemptive manner on the shared resource while viewing the worst-case latency a task may experience on the CPU cores as suspension delays. We develop a rather comprehensive set of task partitioning algorithms that partition tasks onto the shared resource with the objective of guaranteeing schedulability while minimizing the required size of the shared resource, which plays a critical role in reducing the overall cost and complexity of building resource-constrained embedded systems in many application domains. A GPU-based prototype case study and extensive simulation-based experiments have been conducted, which validate both our shared-resource-centric scheduling philosophy and the efficiency of our suspension-based partitioning solutions in practice. },
}

@inproceedings { DBLP:conf/rtss/ChenBSU18,
  author = {Chen, Jian-Jia and Br\"uggen, Georg von der and Shi, Junjie and Ueter, Niklas},
  title = {Dependency Graph Approach for Multiprocessor Real-Time Synchronization},
  booktitle = {IEEE Real-Time Systems Symposium, RTSS 2018},
  year = {2018},
  pages = {434--446},
  address = {Nashville, TN, USA},
  month = {December 11-14},
  url = {https://doi.org/10.1109/RTSS.2018.00057},
  keywords = {georg, junjie},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2018-rtss-jj.pdf},
  confidential = {n},
  abstract = {Over the years, many multiprocessor locking protocols have been designed and analyzed. However, the performance
of these protocols highly depends on how the tasks are partitioned and prioritized, and how the resources are shared locally and globally. This paper answers a few fundamental questions when real-time tasks share resources in multiprocessor systems. We explore the fundamental difficulty of the multiprocessor synchronization problem and show that a very simplified version of this problem is N P -hard in the strong sense regardless of the number of processors and the underlying scheduling paradigm. Therefore, the allowance of preemption or migration does not reduce the computational complexity. On the positive side, we develop a dependency-graph approach that is specifically useful
for frame-based real-time tasks, i.e., when all tasks have the same period and release their jobs always at the same time. We present a series of algorithms with speedup factors between 2 and 3 under semi-partitioned scheduling. We further explore methodologies for and tradeoffs between preemptive and non-preemptive scheduling algorithms, and partitioned and semi-partitioned scheduling algorithms. Our approach is extended to periodic tasks under certain conditions. },
}

@inproceedings { OSPERT17,
  author = {Shi, Junjie and Chen, Kuan-Hsun and Zhao, Shuai and Huang, Wen-Hung and Chen, Jian-Jia and Wellings, Andy},
  title = {Implementation and Evaluation of Multiprocessor Resource Synchronization Protocol (MrsP) on LITMUSRT},
  booktitle = {13th Workshop on Operating Systems Platforms for Embedded Real-Time Applications},
  year = {2017},
  keywords = {kuan, junjie},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-junjie-ospert.pdf},
  confidential = {n},
  abstract = {Preventing race conditions or data corruptions for concurrent shared resource accesses of real-time tasks is a challenging problem. By adopting the resource synchronization protocols, such a problem has been studied in the literature, but there are not enough evaluations that consider the overhead from the implementations of different protocols. In this paper, we discuss our implementation of the Multiprocessor Resource Sharing Protocol (MrsP) and the Distributed Non-Preemptive Protocol (DNPP) on LITMUS RT . Both of them are released in open source under GNU General Public License (GPL2). To study the impact of the implementation overhead, we deploy different synchronization scenarios with generated task sets and measure the performance with respect to the worst-case response time. The results illustrate that generally the implementation overhead is acceptable, whereas some unexpected system overhead may happen under distributed synchronization protocols on LITMUSRT.},
}

@mastersthesis { junjie2016,
  title = {Implementation and Evaluation of Real-Time Multiprocessor Scheduling Algorithms on LITMUS-RT},
  author = {Shi, Junjie},
  school = {TU Dortmund},
  year = {2016},
  month = {December},
  keywords = {junjie},
  confidential = {n},
  adviser = {Prof. Dr. Jian-Jia Chen, M. Ing. Kevin Wen-Hung Huang},
}

@inproceedings { DBLP:conf/rtcsa/WangCST09,
  author = {Wang, Shengquan and Chen, Jian-Jia and Shi, Zhenjun and Thiele, Lothar},
  title = {Energy-Efficient Speed Scheduling for Real-Time Tasks under Thermal Constraints},
  booktitle = {15th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2009, Beijing, China, 24-26 August 2009},
  date-modified = {2015-08-27 13:27:02 +0000},
  year = {2009},
  bdsk-url-1 = {http://doi.ieeecomputersociety.org/10.1109/RTCSA.2009.29},
  pages = {201-209},
  url = {http://doi.ieeecomputersociety.org/10.1109/RTCSA.2009.29},
  keywords = {jj-old},
  confidential = {n},
  abstract = {Thermal constraints have limited the performance improvement of modern computing systems in recent years. As a system could fail if the peak temperature exceeds its thermal constraint, overheating should be avoided while designing a system. Moreover, higher temperature also leads to higher leakage power consumption. This paper explores dynamic thermal management to minimize the energy consumption for a specified computing demand under the thermal constraint. We develop energy-efficient speed scheduling schemes for frame-based real-time tasks under thermal constraints. Experimental results reveal the effectiveness of the proposed scheme in terms of energy consumption in comparison with the reactive schemes in the literature.},
}