Pub Date : 2021-02-05DOI: 10.1007/s11241-020-09361-0
Catherine E. Nemitz, Tanya Amert, Manish Goyal, James H. Anderson
{"title":"Concurrency groups: a new way to look at real-time multiprocessor lock nesting","authors":"Catherine E. Nemitz, Tanya Amert, Manish Goyal, James H. Anderson","doi":"10.1007/s11241-020-09361-0","DOIUrl":"https://doi.org/10.1007/s11241-020-09361-0","url":null,"abstract":"","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"57 1","pages":"190 - 226"},"PeriodicalIF":1.3,"publicationDate":"2021-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s11241-020-09361-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42040429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-05DOI: 10.1007/s11241-021-09363-6
Yeqiong Song, C. D. Gill
{"title":"Guest Editorial: Special issue on outstanding papers from RTNS 2019","authors":"Yeqiong Song, C. D. Gill","doi":"10.1007/s11241-021-09363-6","DOIUrl":"https://doi.org/10.1007/s11241-021-09363-6","url":null,"abstract":"","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"57 1","pages":"95 - 96"},"PeriodicalIF":1.3,"publicationDate":"2021-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s11241-021-09363-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47683167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-18DOI: 10.1007/s11241-020-09360-1
Sergey Voronov, James H. Anderson, Kecheng Yang
Fixed-priority multiprocessor schedulers are often preferable to dynamic-priority ones because they entail less overhead, are easier to implement, and enable certain tasks to be favored over others. Under global fixed-priority (G-FP) scheduling, as applied to the standard sporadic task model, response times for low-priority tasks may be unbounded, even if the total task system utilization is low. In this paper, it is shown that this negative result can be circumvented if different jobs of the same task are allowed to execute in parallel. In particular, a response-time bound is presented for task systems that allow intra-task parallelism. This bound merely requires that the total utilization does not exceed the overall processing capacity—individual task utilizations need not be further restricted. This result implies that G-FP is optimal for scheduling soft real-time tasks that require bounded tardiness, if intra-task parallelism is allowed.
{"title":"Tardiness bounds for fixed-priority global scheduling without intra-task precedence constraints","authors":"Sergey Voronov, James H. Anderson, Kecheng Yang","doi":"10.1007/s11241-020-09360-1","DOIUrl":"https://doi.org/10.1007/s11241-020-09360-1","url":null,"abstract":"<p>Fixed-priority multiprocessor schedulers are often preferable to dynamic-priority ones because they entail less overhead, are easier to implement, and enable certain tasks to be favored over others. Under global fixed-priority (G-FP) scheduling, as applied to the standard sporadic task model, response times for low-priority tasks may be unbounded, even if the total task system utilization is low. In this paper, it is shown that this negative result can be circumvented if different jobs of the same task are allowed to execute in parallel. In particular, a response-time bound is presented for task systems that allow intra-task parallelism. This bound merely requires that the total utilization does not exceed the overall processing capacity—individual task utilizations need not be further restricted. This result implies that G-FP is optimal for scheduling soft real-time tasks that require bounded tardiness, if intra-task parallelism is allowed.</p>","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"224 3","pages":""},"PeriodicalIF":1.3,"publicationDate":"2021-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1007/s11241-020-09356-x
Shaolin Yu, Jihong Zhu, Jiali Yang
For reaching deterministic self-stabilising distributed synchronisation with commercial-off-the-shelf (COTS) Ethernet, this paper explores the Wire-Adapted Linker-Decoupled EtherNet (WALDEN) architecture with the integration of several mass-produced COTS products. Upon this architecture, basic strategies of distributed synchronisation are discussed. Self-stabilising algorithms are presented and formally analysed. Besides, a prototype system is realised with COTS switches, PHY chips, and low-end ARM series under the WALDEN architecture with a minimum hardware modification. The experimental result shows that a sub-microsecond synchronisation precision can be achieved with this prototype implementation even in the presence of low-quality switch with non-queuing delay-jitters of several microseconds. Among existing solutions, this work features in considering the distributed synchronisation, backward-compatibility, and self-stabilisation problems as a whole.
{"title":"Reaching self-stabilising distributed synchronisation with COTS Ethernet components: the WALDEN approach","authors":"Shaolin Yu, Jihong Zhu, Jiali Yang","doi":"10.1007/s11241-020-09356-x","DOIUrl":"https://doi.org/10.1007/s11241-020-09356-x","url":null,"abstract":"For reaching deterministic self-stabilising distributed synchronisation with commercial-off-the-shelf (COTS) Ethernet, this paper explores the Wire-Adapted Linker-Decoupled EtherNet (WALDEN) architecture with the integration of several mass-produced COTS products. Upon this architecture, basic strategies of distributed synchronisation are discussed. Self-stabilising algorithms are presented and formally analysed. Besides, a prototype system is realised with COTS switches, PHY chips, and low-end ARM series under the WALDEN architecture with a minimum hardware modification. The experimental result shows that a sub-microsecond synchronisation precision can be achieved with this prototype implementation even in the presence of low-quality switch with non-queuing delay-jitters of several microseconds. Among existing solutions, this work features in considering the distributed synchronisation, backward-compatibility, and self-stabilisation problems as a whole.","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"225 3","pages":""},"PeriodicalIF":1.3,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1007/s11241-020-09358-9
James Orr, Sanjoy Baruah
The elastic task model enables the adaptation of systems of recurrent real-time tasks under uncertain or potentially overloaded conditions. A range of permissible periods is specified for each task in this model; during run-time a period is selected for each task from the specified range of permissible periods to ensure schedulability in a manner that maximizes the quality of provided service. This model was originally defined for sequential tasks executing upon a preemptive uniprocessor platform; here we consider the implementation of sequential tasks upon multiprocessor platforms. We define algorithms for scheduling sequential elastic tasks under the global and partitioned paradigms of multiprocessor scheduling for both dynamic and static-priority tasks, and we provide an extensive simulation-based comparison of the different approaches.
{"title":"Algorithms for implementing elastic tasks on multiprocessor platforms: a comparative evaluation","authors":"James Orr, Sanjoy Baruah","doi":"10.1007/s11241-020-09358-9","DOIUrl":"https://doi.org/10.1007/s11241-020-09358-9","url":null,"abstract":"The elastic task model enables the adaptation of systems of recurrent real-time tasks under uncertain or potentially overloaded conditions. A range of permissible periods is specified for each task in this model; during run-time a period is selected for each task from the specified range of permissible periods to ensure schedulability in a manner that maximizes the quality of provided service. This model was originally defined for sequential tasks executing upon a preemptive uniprocessor platform; here we consider the implementation of sequential tasks upon multiprocessor platforms. We define algorithms for scheduling sequential elastic tasks under the global and partitioned paradigms of multiprocessor scheduling for both dynamic and static-priority tasks, and we provide an extensive simulation-based comparison of the different approaches.","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"225 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1007/s11241-020-09359-8
Clara Hobbs, Zelin Tong, Joshua Bakita, James H. Anderson
Semi-partitioned scheduling is an approach to multiprocessor real-time scheduling where most tasks are fixed to processors, while a small subset of tasks is allowed to migrate. This approach offers reduced overhead compared to global scheduling, and can reduce processor capacity loss compared to partitioned scheduling. Prior work has resulted in a number of semi-partitioned scheduling algorithms, but their correctness typically hinges on a complex intertwining of offline task assignment and online execution. This brittleness has resulted in few proposed semi-partitioned scheduling algorithms that support dynamic task systems, where tasks may join or leave the system at runtime, and few that are optimal in any sense. This paper introduces EDF-sc, the first semi-partitioned scheduling algorithm that is optimal for scheduling (static) soft real-time (SRT) sporadic task systems and allows tasks to dynamically join and leave. The SRT notion of optimality provided by EDF-sc requires deadline tardiness to be bounded for any task system that does not cause over-utilization. In the event that all tasks can be assigned as fixed, EDF-sc behaves exactly as partitioned EDF. Heuristics are provided that give EDF-sc the novel ability to stabilize the workload to approach the partitioned case as tasks join and leave the system.
{"title":"Statically optimal dynamic soft real-time semi-partitioned scheduling","authors":"Clara Hobbs, Zelin Tong, Joshua Bakita, James H. Anderson","doi":"10.1007/s11241-020-09359-8","DOIUrl":"https://doi.org/10.1007/s11241-020-09359-8","url":null,"abstract":"Semi-partitioned scheduling is an approach to multiprocessor real-time scheduling where most tasks are fixed to processors, while a small subset of tasks is allowed to migrate. This approach offers reduced overhead compared to global scheduling, and can reduce processor capacity loss compared to partitioned scheduling. Prior work has resulted in a number of semi-partitioned scheduling algorithms, but their correctness typically hinges on a complex intertwining of offline task assignment and online execution. This brittleness has resulted in few proposed semi-partitioned scheduling algorithms that support dynamic task systems, where tasks may join or leave the system at runtime, and few that are optimal in any sense. This paper introduces EDF-sc, the first semi-partitioned scheduling algorithm that is optimal for scheduling (static) soft real-time (SRT) sporadic task systems and allows tasks to dynamically join and leave. The SRT notion of optimality provided by EDF-sc requires deadline tardiness to be bounded for any task system that does not cause over-utilization. In the event that all tasks can be assigned as fixed, EDF-sc behaves exactly as partitioned EDF. Heuristics are provided that give EDF-sc the novel ability to stabilize the workload to approach the partitioned case as tasks join and leave the system.","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"225 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-11DOI: 10.1007/s11241-020-09357-w
I. Hussain, Muhammad Ali Awan, P. Souto, K. Bletsas, B. Akesson, E. Tovar
{"title":"Response time analysis of multiframe mixed-criticality systems with arbitrary deadlines","authors":"I. Hussain, Muhammad Ali Awan, P. Souto, K. Bletsas, B. Akesson, E. Tovar","doi":"10.1007/s11241-020-09357-w","DOIUrl":"https://doi.org/10.1007/s11241-020-09357-w","url":null,"abstract":"","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"57 1","pages":"141 - 189"},"PeriodicalIF":1.3,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s11241-020-09357-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47705652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-23DOI: 10.1007/s11241-020-09355-y
Mitra Mahdiani, Alejandro Masrur
In this paper, we are concerned with scheduling a mix of high-criticality (HI) and low-criticality (LO) tasks under Earliest Deadline First (EDF) on one processor. To this end, the system implements two operation modes, LO and HI mode. In LO mode, HI tasks execute for no longer than their optimistic execution budgets and are scheduled together with the LO tasks. The system switches to HI mode, where all LO tasks are prevented from running, when one or more HI tasks run for longer than expected. Since these mode changes may happen at arbitrary points in time, it is difficult to find an accurate bound on carry-over jobs, i.e., those HI jobs that were released before, but did not finish executing at the point of the transition. To overcome this problem, we propose a technique that works around the computation of carry-over execution demand. Basically, the proposed technique separates the schedulability analysis of the transition between LO and HI mode from that of stable HI mode. We prove that a transition from LO to HI mode is feasible, if an equivalent task set derived from the original is schedulable under plain EDF. On this basis, we can apply approximation techniques such as, e.g., the well-known Devi’s test to derive further tests that trade off accuracy versus complexity/runtime. Finally, we perform a detailed comparison with respect to weighted schedulability on synthetic data illustrating benefits by the proposed technique.
{"title":"A novel view on bounding execution demand under mixed-criticality EDF","authors":"Mitra Mahdiani, Alejandro Masrur","doi":"10.1007/s11241-020-09355-y","DOIUrl":"https://doi.org/10.1007/s11241-020-09355-y","url":null,"abstract":"In this paper, we are concerned with scheduling a mix of high-criticality (HI) and low-criticality (LO) tasks under Earliest Deadline First (EDF) on one processor. To this end, the system implements two operation modes, LO and HI mode. In LO mode, HI tasks execute for no longer than their optimistic execution budgets and are scheduled together with the LO tasks. The system switches to HI mode, where all LO tasks are prevented from running, when one or more HI tasks run for longer than expected. Since these mode changes may happen at arbitrary points in time, it is difficult to find an accurate bound on carry-over jobs, i.e., those HI jobs that were released before, but did not finish executing at the point of the transition. To overcome this problem, we propose a technique that works around the computation of carry-over execution demand. Basically, the proposed technique separates the schedulability analysis of the transition between LO and HI mode from that of stable HI mode. We prove that a transition from LO to HI mode is feasible, if an equivalent task set derived from the original is schedulable under plain EDF. On this basis, we can apply approximation techniques such as, e.g., the well-known Devi’s test to derive further tests that trade off accuracy versus complexity/runtime. Finally, we perform a detailed comparison with respect to weighted schedulability on synthetic data illustrating benefits by the proposed technique.","PeriodicalId":54507,"journal":{"name":"Real-Time Systems","volume":"226 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2020-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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