Volume
LIPIcs, Volume 196
33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)
-
Part of:
Series:
Leibniz International Proceedings in Informatics (LIPIcs)
Conference: Euromicro Conference on Real-Time Systems (ECRTS)
Event
ECRTS 2021, July 5-9, 2021, Virtual ConferenceEditor
Publication Details
- published at: 2021-06-30
- Publisher: Schloss Dagstuhl – Leibniz-Zentrum für Informatik
- ISBN: 978-3-95977-192-4
- DBLP: db/conf/ecrts/ecrts2021
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Document
Complete Volume
LIPIcs, Volume 196, ECRTS 2021, Complete Volume
Abstract
LIPIcs, Volume 196, ECRTS 2021, Complete Volume
Cite as
33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 1-370, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@Proceedings{brandenburg:LIPIcs.ECRTS.2021,
title = {{LIPIcs, Volume 196, ECRTS 2021, Complete Volume}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {1--370},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021},
URN = {urn:nbn:de:0030-drops-139309},
doi = {10.4230/LIPIcs.ECRTS.2021},
annote = {Keywords: LIPIcs, Volume 196, ECRTS 2021, Complete Volume}
}
Document
Front Matter
Front Matter, Table of Contents, Preface, Conference Organization
Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as
33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 0:i-0:xii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{brandenburg:LIPIcs.ECRTS.2021.0,
author = {Brandenburg, Bj\"{o}rn B.},
title = {{Front Matter, Table of Contents, Preface, Conference Organization}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {0:i--0:xii},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.0},
URN = {urn:nbn:de:0030-drops-139317},
doi = {10.4230/LIPIcs.ECRTS.2021.0},
annote = {Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
Vicuna: A Timing-Predictable RISC-V Vector Coprocessor for Scalable Parallel Computation
Abstract
In this work, we present Vicuna, a timing-predictable vector coprocessor. A vector processor can be scaled to satisfy the performance requirements of massively parallel computation tasks, yet its timing behavior can remain simple enough to be efficiently analyzable. Therefore, vector processors are promising for highly parallel real-time applications, such as advanced driver assistance systems and autonomous vehicles. Vicuna has been specifically tailored to address the needs of real-time applications. It features predictable and repeatable timing behavior and is free of timing anomalies, thus enabling effective and tight worst-case execution time (WCET) analysis while retaining the performance and efficiency commonly seen in other vector processors. We demonstrate our architecture’s predictability, scalability, and performance by running a set of benchmark applications on several configurations of Vicuna synthesized on a Xilinx 7 Series FPGA with a peak performance of over 10 billion 8-bit operations per second, which is in line with existing non-predictable soft vector-processing architectures.
Cite as
Michael Platzer and Peter Puschner. Vicuna: A Timing-Predictable RISC-V Vector Coprocessor for Scalable Parallel Computation. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 1:1-1:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{platzer_et_al:LIPIcs.ECRTS.2021.1,
author = {Platzer, Michael and Puschner, Peter},
title = {{Vicuna: A Timing-Predictable RISC-V Vector Coprocessor for Scalable Parallel Computation}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {1:1--1:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.1},
URN = {urn:nbn:de:0030-drops-139323},
doi = {10.4230/LIPIcs.ECRTS.2021.1},
annote = {Keywords: Real-time Systems, Vector Processors, RISC-V}
}
Document
A Memory Scheduling Infrastructure for Multi-Core Systems with Re-Programmable Logic
Abstract
The sharp increase in demand for performance has prompted an explosion in the complexity of modern multi-core embedded systems. This has lead to unprecedented temporal unpredictability concerns in Cyber-Physical Systems (CPS). On-chip integration of programmable logic (PL) alongside a conventional Processing System (PS) in modern Systems-on-Chip (SoC) establishes a genuine compromise between specialization, performance, and reconfigurability. In addition to typical use-cases, it has been shown that the PL can be used to observe, manipulate, and ultimately manage memory traffic generated by a traditional multi-core processor.
This paper explores the possibility of PL-aided memory scheduling by proposing a Scheduler In-the-Middle (SchIM). We demonstrate that the SchIM enables transaction-level control over the main memory traffic generated by a set of embedded cores. Focusing on extensibility and reconfigurability, we put forward a SchIM design covering two main objectives. First, to provide a safe playground to test innovative memory scheduling mechanisms; and second, to establish a transition path from software-based memory regulation to provably correct hardware-enforced memory scheduling. We evaluate our design through a full-system implementation on a commercial PS-PL platform using synthetic and real-world benchmarks.
Cite as
Denis Hoornaert, Shahin Roozkhosh, and Renato Mancuso. A Memory Scheduling Infrastructure for Multi-Core Systems with Re-Programmable Logic. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 2:1-2:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{hoornaert_et_al:LIPIcs.ECRTS.2021.2,
author = {Hoornaert, Denis and Roozkhosh, Shahin and Mancuso, Renato},
title = {{A Memory Scheduling Infrastructure for Multi-Core Systems with Re-Programmable Logic}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {2:1--2:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.2},
URN = {urn:nbn:de:0030-drops-139331},
doi = {10.4230/LIPIcs.ECRTS.2021.2},
annote = {Keywords: Memory Scheduling, PLIM, FPGA, Memory Management, Bandwidth Regulation, MemGuard, Coloring, Bank Partitioning, Real-time, Multicore, Safety-critical}
}
Document
Leveraging Hardware QoS to Control Contention in the Xilinx Zynq UltraScale+ MPSoC
Abstract
The interference co-running tasks generate on each other’s timing behavior continues to be one of the main challenges to be addressed before Multi-Processor System-on-Chip (MPSoCs) are fully embraced in critical systems like those deployed in avionics and automotive domains. Modern MPSoCs like the Xilinx Zynq UltraScale+ incorporate hardware Quality of Service (QoS) mechanisms that can help controlling contention among tasks. Given the distributed nature of modern MPSoCs, the route a request follows from its source (usually a compute element like a CPU) to its target (usually a memory) crosses several QoS points, each one potentially implementing a different QoS mechanism. Mastering QoS mechanisms individually, as well as their combined operation, is pivotal to obtain the expected benefits from the QoS support. In this work, we perform, to our knowledge, the first qualitative and quantitative analysis of the distributed QoS mechanisms in the Xilinx UltraScale+ MPSoC. We empirically derive QoS information not covered by the technical documentation, and show limitations and benefits of the available QoS support. To that end, we use a case study building on neural network kernels commonly used in autonomous systems in different real-time domains.
Cite as
Alejandro Serrano-Cases, Juan M. Reina, Jaume Abella, Enrico Mezzetti, and Francisco J. Cazorla. Leveraging Hardware QoS to Control Contention in the Xilinx Zynq UltraScale+ MPSoC. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 3:1-3:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{serranocases_et_al:LIPIcs.ECRTS.2021.3,
author = {Serrano-Cases, Alejandro and Reina, Juan M. and Abella, Jaume and Mezzetti, Enrico and Cazorla, Francisco J.},
title = {{Leveraging Hardware QoS to Control Contention in the Xilinx Zynq UltraScale+ MPSoC}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {3:1--3:26},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.3},
URN = {urn:nbn:de:0030-drops-139340},
doi = {10.4230/LIPIcs.ECRTS.2021.3},
annote = {Keywords: Quality of Service, Real-Time Systems, MPSoC, Multicore Contention}
}
Document
Governing with Insights: Towards Profile-Driven Cache Management of Black-Box Applications
Abstract
There exists a divide between the ever-increasing demand for high-performance embedded systems and the availability of practical methodologies to understand the interplay of complex data-intensive applications with hardware memory resources. On the one hand, traditional static analysis approaches are seldomly applicable to latest-generation multi-core platforms due to a lack of accurate micro-architectural models. On the other hand, measurement-based methods only provide coarse-grained information about the end-to-end execution of a given real-time application.
In this paper, we describe a novel methodology, namely Black-Box Profiling (BBProf), to gather fine-grained insights on the usage of cache resources in applications of realistic complexity. The goal of our technique is to extract the relative importance of individual memory pages towards the overall temporal behavior of a target application. Importantly, BBProf does not require the semantics of the target application to be known - i.e., applications are treated as black-boxes - and it does not rely on any platform-specific hardware support. We provide an open-source full-system implementation and showcase how BBProf can be used to perform profile-driven cache management.
Cite as
Golsana Ghaemi, Dharmesh Tarapore, and Renato Mancuso. Governing with Insights: Towards Profile-Driven Cache Management of Black-Box Applications. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 4:1-4:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{ghaemi_et_al:LIPIcs.ECRTS.2021.4,
author = {Ghaemi, Golsana and Tarapore, Dharmesh and Mancuso, Renato},
title = {{Governing with Insights: Towards Profile-Driven Cache Management of Black-Box Applications}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {4:1--4:25},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.4},
URN = {urn:nbn:de:0030-drops-139359},
doi = {10.4230/LIPIcs.ECRTS.2021.4},
annote = {Keywords: Cache Profiling, WSS Estimation, Cache Interference, Real-time, Multicore, Contention-induced Instruction Stall, C2IS, Coloring, Cache Management, Cacheability}
}
Document
nDimNoC: Real-Time D-dimensional NoC
Abstract
The growing demand of powerful embedded systems to perform advanced functionalities led to a large increase in the number of computation nodes integrated in Systems-on-chip (SoC). In this context, network-on-chips (NoCs) emerged as a new standard communication infrastructure for multi-processor SoCs (MPSoCs). In this work, we present nDimNoC, a new D-dimensional NoC that provides real-time guarantees for systems implemented upon MPSoCs. Specifically, (1) we propose a new router architecture and a new deflection-based routing policy that use the properties of circulant topologies to ensure bounded worst-case communication delays, and (2) we develop a generic worst-case communication time (WCCT) analysis for packets transmitted over nDimNoC. In our experiments, we show that the WCCT of packets decreases when we increase the dimensionality of the NoC using nDimNoC’s topolgy and routing policy. By implementing nDimNoC in Verilog and synthesizing it for an FPGA platform, we show that a 3D-nDimNoC requires ≈5-times less silicon than routers that use virtual channels (VC). We computed the maximum operating frequency of a 3D-nDimNoC with Xilinx Vivado. Increasing the number dimensions in the NoC improves WCCT at the cost of a more complex routing logic that may result in a reduced operating clock frequency.
Cite as
Yilian Ribot González, Geoffrey Nelissen, and Eduardo Tovar. nDimNoC: Real-Time D-dimensional NoC. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 5:1-5:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{ribotgonzalez_et_al:LIPIcs.ECRTS.2021.5,
author = {Ribot Gonz\'{a}lez, Yilian and Nelissen, Geoffrey and Tovar, Eduardo},
title = {{nDimNoC: Real-Time D-dimensional NoC}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {5:1--5:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.5},
URN = {urn:nbn:de:0030-drops-139363},
doi = {10.4230/LIPIcs.ECRTS.2021.5},
annote = {Keywords: Real-Time Embedded Systems, Systems-on-Chips, Network-on-Chips, Worst-Case Communication Time}
}
Document
Light Reading: Optimizing Reader/Writer Locking for Read-Dominant Real-Time Workloads
Abstract
This paper is directed at reader/writer locking for read-dominant real-time workloads. It is shown that state-of-the-art real-time reader/writer locking protocols are subject to performance limitations when reads dominate, and that existing schedulability analysis fails to leverage the sparsity of writes in this case. A new reader/writer locking-protocol implementation and new inflation-free schedulability analysis are proposed to address these problems. Overhead evaluations of the new implementation show a decrease in overheads of up to 70% over previous implementations, leading to throughput for read operations increasing by up to 450%. Schedulability experiments are presented that show that the analysis results in schedulability improvements of up to 156.8% compared to the existing state-of-the-art approach.
Cite as
Catherine E. Nemitz, Shai Caspin, James H. Anderson, and Bryan C. Ward. Light Reading: Optimizing Reader/Writer Locking for Read-Dominant Real-Time Workloads. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 6:1-6:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{nemitz_et_al:LIPIcs.ECRTS.2021.6,
author = {Nemitz, Catherine E. and Caspin, Shai and Anderson, James H. and Ward, Bryan C.},
title = {{Light Reading: Optimizing Reader/Writer Locking for Read-Dominant Real-Time Workloads}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {6:1--6:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.6},
URN = {urn:nbn:de:0030-drops-139378},
doi = {10.4230/LIPIcs.ECRTS.2021.6},
annote = {Keywords: Reader/writer, real-time, synchronization, spinlock, RMR complexity}
}
Document
Schedulability Analysis for Multi-Core Systems Accounting for Resource Stress and Sensitivity
Abstract
Timing verification of multi-core systems is complicated by contention for shared hardware resources between co-running tasks on different cores. This paper introduces the Multi-core Resource Stress and Sensitivity (MRSS) task model that characterizes how much stress each task places on resources and how much it is sensitive to such resource stress. This model facilitates a separation of concerns, thus retaining the advantages of the traditional two-step approach to timing verification (i.e. timing analysis followed by schedulability analysis). Response time analysis is derived for the MRSS task model, providing efficient context-dependent and context independent schedulability tests for both fixed priority preemptive and fixed priority non-preemptive scheduling. Dominance relations are derived between the tests, and proofs of optimal priority assignment provided. The MRSS task model is underpinned by a proof-of-concept industrial case study.
Cite as
Robert I. Davis, David Griffin, and Iain Bate. Schedulability Analysis for Multi-Core Systems Accounting for Resource Stress and Sensitivity. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 7:1-7:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{davis_et_al:LIPIcs.ECRTS.2021.7,
author = {Davis, Robert I. and Griffin, David and Bate, Iain},
title = {{Schedulability Analysis for Multi-Core Systems Accounting for Resource Stress and Sensitivity}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {7:1--7:26},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.7},
URN = {urn:nbn:de:0030-drops-139388},
doi = {10.4230/LIPIcs.ECRTS.2021.7},
annote = {Keywords: real-time, multi-core, scheduling, schedulability analysis, cross-core contention, resource stress, resource sensitivity}
}
Document
Response Time Bounds for DAG Tasks with Arbitrary Intra-Task Priority Assignment
Abstract
Most parallel real-time applications can be modeled as directed acyclic graph (DAG) tasks. Intra-task priority assignment can reduce the nondeterminism of runtime behavior of DAG tasks, possibly resulting in a smaller worst-case response time. However, intra-task priority assignment incurs dependencies between different parts of the graph, making it a challenging problem to compute the response time bound. Existing work on intra-task task priority assignment for DAG tasks is subject to the constraint that priority assignment must comply with the topological order of the graph, so that the response time bound can be computed in polynomial time. In this paper, we relax this constraint and propose a new method to compute response time bound of DAG tasks with arbitrary priority assignment. With the benefit of our new method, we present a simple but effective priority assignment policy, leading to smaller response time bounds. Comprehensive evaluation with both single-DAG systems and multi-DAG systems demonstrates that our method outperforms the state-of-the-art method with a considerable margin.
Cite as
Qingqiang He, Mingsong Lv, and Nan Guan. Response Time Bounds for DAG Tasks with Arbitrary Intra-Task Priority Assignment. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 8:1-8:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{he_et_al:LIPIcs.ECRTS.2021.8,
author = {He, Qingqiang and Lv, Mingsong and Guan, Nan},
title = {{Response Time Bounds for DAG Tasks with Arbitrary Intra-Task Priority Assignment}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {8:1--8:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.8},
URN = {urn:nbn:de:0030-drops-139394},
doi = {10.4230/LIPIcs.ECRTS.2021.8},
annote = {Keywords: real-time systems, response time bound, DAG tasks, intra-task priority assignment}
}
Document
Graceful Degradation in Semi-Clairvoyant Scheduling
Abstract
In the Vestal model of mixed-criticality systems, jobs are characterized by multiple different estimates of their actual, but unknown, worst-case execution time (WCET) parameters. Some recent research has focused upon a semi-clairvoyant model for mixed-criticality systems in which it is assumed that each job reveals upon arrival which of its WCET parameters it will respect. We study the problem of scheduling such semi-clairvoyant systems to ensure graceful degradation of service to less critical jobs in the event that the systems exhibit high-criticality behavior. We propose multiple different interpretations of graceful degradation in such systems, and derive efficient scheduling algorithms that are capable of ensuring graceful degradation under these different interpretations.
Cite as
Sanjoy Baruah and Pontus Ekberg. Graceful Degradation in Semi-Clairvoyant Scheduling. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 9:1-9:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{baruah_et_al:LIPIcs.ECRTS.2021.9,
author = {Baruah, Sanjoy and Ekberg, Pontus},
title = {{Graceful Degradation in Semi-Clairvoyant Scheduling}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {9:1--9:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.9},
URN = {urn:nbn:de:0030-drops-139404},
doi = {10.4230/LIPIcs.ECRTS.2021.9},
annote = {Keywords: Mixed criticality, semi-clairvoyance, graceful degradation}
}
Document
Hard Real-Time Stationary GANG-Scheduling
Abstract
The scheduling of parallel real-time tasks enables the efficient utilization of modern multiprocessor platforms for systems with real-time constrains. In this situation, the gang task model, in which each parallel sub-job has to be executed simultaneously, has shown significant performance benefits due to reduced context switches and more efficient intra-task synchronization.
In this paper, we provide the first schedulability analysis for sporadic constrained-deadline gang task systems and propose a novel stationary gang scheduling algorithm. We show that the schedulability problem of gang task sets can be reduced to the uniprocessor self-suspension schedulability problem. Furthermore, we provide a class of partitioning algorithms to find a stationary gang assignment and show that it bounds the worst-case interference of each task. To demonstrate the effectiveness of our proposed approach, we evaluate it for implicit-deadline systems using randomized task sets under different settings, showing that our approach outperforms the state-of-the-art.
Cite as
Niklas Ueter, Mario Günzel, Georg von der Brüggen, and Jian-Jia Chen. Hard Real-Time Stationary GANG-Scheduling. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 10:1-10:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{ueter_et_al:LIPIcs.ECRTS.2021.10,
author = {Ueter, Niklas and G\"{u}nzel, Mario and von der Br\"{u}ggen, Georg and Chen, Jian-Jia},
title = {{Hard Real-Time Stationary GANG-Scheduling}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {10:1--10:19},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.10},
URN = {urn:nbn:de:0030-drops-139410},
doi = {10.4230/LIPIcs.ECRTS.2021.10},
annote = {Keywords: Real-Time Systems, Gang Scheduling, Parallel Computing, Scheduling Algorithms}
}
Document
Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers
Abstract
The global earliest-deadline-first (GEDF) scheduler and its variants are soft-real-time (SRT) optimal for periodic/sporadic tasks, meaning they provide bounded tardiness so long as the underlying platform is not over-utilized. Although their SRT-optimality has long been known, tight tardiness bounds for these schedulers have remained elusive. In this paper, a tardiness bound, that does not depend on the processor or task count, is derived for pseudo-harmonic periodic tasks, which are commonly used in practice, under global-EDF-like (GEL) schedulers. This class of schedulers includes both GEDF and first-in-first-out (FIFO). This bound is shown to be generally tight via an example. Furthermore, it is shown that exact tardiness bounds for GEL-scheduled pseudo-harmonic periodic tasks can be computed in pseudo-polynomial time.
Cite as
Shareef Ahmed and James H. Anderson. Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 11:1-11:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{ahmed_et_al:LIPIcs.ECRTS.2021.11,
author = {Ahmed, Shareef and Anderson, James H.},
title = {{Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {11:1--11:24},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.11},
URN = {urn:nbn:de:0030-drops-139428},
doi = {10.4230/LIPIcs.ECRTS.2021.11},
annote = {Keywords: soft real-time systems, multicore, tardiness bounds}
}
Document
Feasibility Analysis of Conditional DAG Tasks
Abstract
Feasibility analysis for Conditional DAG tasks (C-DAGs) upon multiprocessor platforms is shown to be complete for the complexity class pspace. It is shown that as a consequence integer linear programming solvers (ILP solvers) are likely to prove inadequate for such analysis. A demarcation is identified between the feasibility-analysis problems on C-DAGs that are efficiently solvable using ILP solvers and those that are not, by characterizing a restricted class of C-DAGs for which feasibility analysis is shown to be efficiently solvable using ILP solvers.
Cite as
Sanjoy Baruah and Alberto Marchetti-Spaccamela. Feasibility Analysis of Conditional DAG Tasks. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 12:1-12:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{baruah_et_al:LIPIcs.ECRTS.2021.12,
author = {Baruah, Sanjoy and Marchetti-Spaccamela, Alberto},
title = {{Feasibility Analysis of Conditional DAG Tasks}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {12:1--12:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.12},
URN = {urn:nbn:de:0030-drops-139433},
doi = {10.4230/LIPIcs.ECRTS.2021.12},
annote = {Keywords: Multiprocessor feasibility analysis, Conditional Directed Acyclic Graphs, PSPACE-complete}
}
Document
Scheduling Replica Voting in Fixed-Priority Real-Time Systems
Abstract
Reliability and safety are mandatory requirements for safety-critical embedded systems. The design of a fault-tolerant system is required in many fields (e.g., railway, automotive, avionics) and redundancy helps in achieving this goal. Redundant systems typically leverage voting techniques applied to the outputs produced by tasks to detect and even tolerate failures.
This paper studies the integration of distributed voting protocols in fixed-priority real-time systems from a scheduling perspective. It analyzes two scheduling strategies for implementing voting. One is attractive and friendly for software developers and based on suspending the task execution until the replica provides the data to be voted. The other one is inspired by the Logical Execution Time (LET) paradigm and requires introducing additional tasks in the system to accomplish voting-related activities. Queuing and delays introduced by inter-replica communication interfaces are also analyzed.
Experimental results are finally presented to compare the two strategies, showing that LET-inspired voting is much more predictable and hence more suitable than the other strategy for fixed-priority real-time systems.
Cite as
Pietro Fara, Gabriele Serra, Alessandro Biondi, and Ciro Donnarumma. Scheduling Replica Voting in Fixed-Priority Real-Time Systems. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 13:1-13:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{fara_et_al:LIPIcs.ECRTS.2021.13,
author = {Fara, Pietro and Serra, Gabriele and Biondi, Alessandro and Donnarumma, Ciro},
title = {{Scheduling Replica Voting in Fixed-Priority Real-Time Systems}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {13:1--13:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.13},
URN = {urn:nbn:de:0030-drops-139449},
doi = {10.4230/LIPIcs.ECRTS.2021.13},
annote = {Keywords: Real-time systems, safety-critical systems, voting, redundancy, fault-tolerance, logical execution time}
}
Document
A Residual Service Curve of Rate-Latency Server Used by Sporadic Flows Computable in Quadratic Time for Network Calculus
Abstract
Computing response times for resources shared by periodic workloads (tasks or data flows) can be very time consuming as it depends on the least common multiple of the periods. In a previous study, a quadratic algorithm was provided to upper bound the response time of a set of periodic tasks with a fixed-priority scheduling. This paper generalises this result by considering a rate-latency server and sporadic workloads and gives a response time and residual curve that can be used in other contexts. It also provides a formal proof in the Coq language.
Cite as
Marc Boyer, Pierre Roux, Hugo Daigmorte, and David Puechmaille. A Residual Service Curve of Rate-Latency Server Used by Sporadic Flows Computable in Quadratic Time for Network Calculus. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 14:1-14:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{boyer_et_al:LIPIcs.ECRTS.2021.14,
author = {Boyer, Marc and Roux, Pierre and Daigmorte, Hugo and Puechmaille, David},
title = {{A Residual Service Curve of Rate-Latency Server Used by Sporadic Flows Computable in Quadratic Time for Network Calculus}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {14:1--14:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.14},
URN = {urn:nbn:de:0030-drops-139457},
doi = {10.4230/LIPIcs.ECRTS.2021.14},
annote = {Keywords: Network Calculus, response time, residual curve, rate-latency server, sporadic workload, formal proof, Coq}
}
Document
Stability and Performance Analysis of Control Systems Subject to Bursts of Deadline Misses
Abstract
Control systems are by design robust to various disturbances, ranging from noise to unmodelled dynamics. Recent work on the weakly hard model - applied to controllers - has shown that control tasks can also be inherently robust to deadline misses. However, existing exact analyses are limited to the stability of the closed-loop system. In this paper we show that stability is important but cannot be the only factor to determine whether the behaviour of a system is acceptable also under deadline misses. We focus on systems that experience bursts of deadline misses and on their recovery to normal operation. We apply the resulting comprehensive analysis (that includes both stability and performance) to a Furuta pendulum, comparing simulated data and data obtained with the real plant. We further evaluate our analysis using a benchmark set composed of 133 systems, which is considered representative of industrial control plants. Our results show the handling of the control signal is an extremely important factor in the performance degradation that the controller experiences - a clear indication that only a stability test does not give enough indication about the robustness to deadline misses.
Cite as
Nils Vreman, Anton Cervin, and Martina Maggio. Stability and Performance Analysis of Control Systems Subject to Bursts of Deadline Misses. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 15:1-15:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{vreman_et_al:LIPIcs.ECRTS.2021.15,
author = {Vreman, Nils and Cervin, Anton and Maggio, Martina},
title = {{Stability and Performance Analysis of Control Systems Subject to Bursts of Deadline Misses}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {15:1--15:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.15},
URN = {urn:nbn:de:0030-drops-139460},
doi = {10.4230/LIPIcs.ECRTS.2021.15},
annote = {Keywords: Fault-Tolerant Control Systems, Weakly Hard Task Model}
}
Document
On the Convolution Efficiency for Probabilistic Analysis of Real-Time Systems
Abstract
This paper addresses two major problems in probabilistic analysis of real-time systems: space and time complexity of convolution of discrete random variables. For years, these two problems have limited the applicability of many methods for the probabilistic analysis of real-time systems, that rely on convolution as the main operation. Convolution in probabilistic analysis leads to a substantial space explosion and therefore space reductions may be necessary to make the problem tractable. However, the reductions lead to pessimism in the obtained probabilistic distributions, affecting the accuracy of the timing analysis. In this paper, we propose an optimal algorithm for down-sampling, which minimises the probabilistic expectation (i.e., the pessimism) in polynomial time. The second problem relates to the time complexity of the convolution between discrete random variables. It has been shown that quadratic time complexity of a single linear convolution, together with the space explosion of probabilistic analysis, limits its applicability for systems with a large number of tasks, jobs, and other analysed entities. In this paper, we show that the problem can be solved with a complexity of 𝒪(n log(n)), by proposing an algorithm that utilises circular convolution and vector space reductions. Evaluation results show several important improvements with respect to other state-of-the-art techniques.
Cite as
Filip Marković, Alessandro Vittorio Papadopoulos, and Thomas Nolte. On the Convolution Efficiency for Probabilistic Analysis of Real-Time Systems. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 16:1-16:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)
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@InProceedings{markovic_et_al:LIPIcs.ECRTS.2021.16,
author = {Markovi\'{c}, Filip and Papadopoulos, Alessandro Vittorio and Nolte, Thomas},
title = {{On the Convolution Efficiency for Probabilistic Analysis of Real-Time Systems}},
booktitle = {33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
pages = {16:1--16:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-192-4},
ISSN = {1868-8969},
year = {2021},
volume = {196},
editor = {Brandenburg, Bj\"{o}rn B.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.16},
URN = {urn:nbn:de:0030-drops-139474},
doi = {10.4230/LIPIcs.ECRTS.2021.16},
annote = {Keywords: Probabilistic analysis, Random variables, Algorithm Complexity}
}