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DOI: 10.4230/LIPIcs.ECRTS.2024.3

Reachability-Based Response-Time Analysis of Preemptive Tasks Under Global Scheduling

Authors: Pourya Gohari, Jeroen Voeten, and Mitra Nasri

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

Global scheduling reduces the average response times as it can use the available computing cores more efficiently for scheduling ready tasks. However, this flexibility poses challenges in accurately quantifying interference scenarios, often resulting in either conservative response-time analyses or scalability issues. In this paper, we present a new response-time analysis for preemptive periodic tasks (or job sets) subject to release jitter under global job-level fixed-priority (JLFP) scheduling. Our analysis relies on the notion of schedule-abstraction graph (SAG), a reachability-based response-time analysis known for its potential accuracy and efficiency. Up to this point, SAG was limited to non-preemptive tasks due to the complexity of handling preemption when the number of preemptions and the moments they occur are not known beforehand. In this paper, we introduce the concept of time partitions and demonstrate how it facilitates the extension of SAG for preemptive tasks. Moreover, our paper provides the first response-time analysis for the global EDF(k) policy - a JLFP scheduling policy introduced in 2003 to address the Dhall’s effect. Our experiments show that our analysis is significantly more accurate compared to the state-of-the-art analyses. For example, we identify 12 times more schedulable task sets than existing tests for the global EDF policy (e.g., for systems with 6 to 16 tasks, 70% utilization, and 4 cores) with an average runtime of 30 minutes. We show that EDF(k) outperforms global RM and EDF by scheduling on average 24.9% more task sets (e.g., for systems with 2 to 10 cores and 70% utilization). Moreover, for the first time, we show that global JLFP scheduling policies (particularly, global EDF(k)) are able to schedule task sets that are not schedulable using well-known partitioning heuristics.

Cite as

Pourya Gohari, Jeroen Voeten, and Mitra Nasri. Reachability-Based Response-Time Analysis of Preemptive Tasks Under Global Scheduling. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 3:1-3:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gohari_et_al:LIPIcs.ECRTS.2024.3,
  author =	{Gohari, Pourya and Voeten, Jeroen and Nasri, Mitra},
  title =	{{Reachability-Based Response-Time Analysis of Preemptive Tasks Under Global Scheduling}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{3:1--3:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.3},
  URN =		{urn:nbn:de:0030-drops-203064},
  doi =		{10.4230/LIPIcs.ECRTS.2024.3},
  annote =	{Keywords: Response-time analysis, global scheduling, preemptive, job-level fixed-priority scheduling policy, multicore, schedule-abstraction graph}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.4

Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis

Authors: Mario Günzel, Georg von der Brüggen, and Jian-Jia Chen

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

Tasks are called self-suspending if they can yield their ready state (specifically, releasing the processor while having highest priority) despite being incomplete, for instance, to offload computation to an external device or when waiting on access rights for shared resources or data. This self-suspending behavior requires special treatment when applying analytical results to compute worst-case response time bounds. One typical treatment is modeling self-suspension as release jitter in a so-called jitter-based analysis. The state of the art, when considering task-level fixed-priority scheduling, individually quantifies the jitter term of each higher-priority task by its worst-case response time minus its worst-case execution time. This work tightens the jitter term by taking the execution behavior of the other higher-priority tasks into account. Our improved jitter-based analysis analytically dominates the previous jitter-based analysis. Moreover, an evaluation for synthetically generated sporadic tasks demonstrates that this jitter term results in tighter worst-case response time bounds for self-suspending tasks. We observe an improvement for up to 55.89 % of the tasksets compared to the previous jitter-based analysis.

Cite as

Mario Günzel, Georg von der Brüggen, and Jian-Jia Chen. Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 4:1-4:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gunzel_et_al:LIPIcs.ECRTS.2024.4,
  author =	{G\"{u}nzel, Mario and von der Br\"{u}ggen, Georg and Chen, Jian-Jia},
  title =	{{Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{4:1--4:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.4},
  URN =		{urn:nbn:de:0030-drops-203074},
  doi =		{10.4230/LIPIcs.ECRTS.2024.4},
  annote =	{Keywords: Worst-Case Response Time, WCRT, Jitter, Self-Suspension, Analysis}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.5

Shared Resource Contention in MCUs: A Reality Check and the Quest for Timeliness

Authors: Daniel Oliveira, Weifan Chen, Sandro Pinto, and Renato Mancuso

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

Microcontrollers (MCUs) are steadily embracing multi-core technology to meet growing performance demands. This trend marks a shift from their traditionally simple, deterministic designs to more complex and inherently less predictable architectures. While shared resource contention is well-studied in mid to high-end embedded systems, the emergence of multi-core architectures in MCUs introduces unique challenges and characteristics that existing research has not fully explored. In this paper, we conduct an in-depth investigation of both mainstream and next-generation MCU-based platforms, aiming to identify the sources of contention on systems typically lacking these problems. We empirically demonstrate substantial contention effects across different MCU architectures (i.e., from single- to multi-core configurations), highlighting significant application slowdowns. Notably, we observe that slowdowns can reach several orders of magnitude, with the most extreme cases showing up to a 3800x (times, not percent) increase in execution time. To address these issues, we propose and evaluate muTPArtc, a novel mechanism designed for Timely Progress Assessment (TPA) and TPA-based runtime control specifically tailored to MCUs. muTPArtc is an MCU-specialized TPA-based mechanism that leverages hardware facilities widely available in commercial off-the-shelf MCUs (i.e., hardware breakpoints and cycle counters) to successfully monitor applications' progress, detect, and mitigate timing violations. Our results demonstrate that muTPArtc effectively manages performance degradation due to interference, requiring only minimal modifications to the build pipeline and no changes to the source code of the target application, while incurring minor overheads.

Cite as

Daniel Oliveira, Weifan Chen, Sandro Pinto, and Renato Mancuso. Shared Resource Contention in MCUs: A Reality Check and the Quest for Timeliness. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 5:1-5:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{oliveira_et_al:LIPIcs.ECRTS.2024.5,
  author =	{Oliveira, Daniel and Chen, Weifan and Pinto, Sandro and Mancuso, Renato},
  title =	{{Shared Resource Contention in MCUs: A Reality Check and the Quest for Timeliness}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{5:1--5:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.5},
  URN =		{urn:nbn:de:0030-drops-203088},
  doi =		{10.4230/LIPIcs.ECRTS.2024.5},
  annote =	{Keywords: multi-core microcontrollers, shared resources contention, progress-aware regulation}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.7

The Omnivisor: A Real-Time Static Partitioning Hypervisor Extension for Heterogeneous Core Virtualization over MPSoCs

Authors: Daniele Ottaviano, Francesco Ciraolo, Renato Mancuso, and Marcello Cinque

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

Following the needs of industrial applications, virtualization has emerged as one of the most effective approaches for the consolidation of mixed-criticality systems while meeting tight constraints in terms of space, weight, power, and cost (SWaP-C). In embedded platforms with homogeneous processors, a wealth of works have proposed designs and techniques to enforce spatio-temporal isolation by leveraging well-understood virtualization support. Unfortunately, achieving the same goal on heterogeneous MultiProcessor Systems-on-Chip (MPSoCs) has been largely overlooked. Modern hypervisors are designed to operate exclusively on main cores, with little or no consideration given to other co-processors within the system, such as small microcontroller-level CPUs or soft-cores deployed on programmable logic (FPGA). Typically, hypervisors consider co-processors as I/O devices allocated to virtual machines that run on primary cores, yielding full control and responsibility over them. Nevertheless, inadequate management of these resources can lead to spatio-temporal isolation issues within the system. In this paper, we propose the Omnivisor model as a paradigm for the holistic management of heterogeneous platforms. The model generalizes the features of real-time static partitioning hypervisors to enable the execution of virtual machines on processors with different Instruction Set Architectures (ISAs) within the same MPSoC. Moreover, the Omnivisor ensures temporal and spatial isolation between virtual machines by integrating and leveraging a variety of hardware and software protection mechanisms. The presented approach not only expands the scope of virtualization in MPSoCs but also enhances the overall system reliability and real-time performance for mixed-criticality applications. A full open-source reference implementation of the Omnivisor based on the Jailhouse hypervisor is provided, targeting ARM real-time processing units and RISC-V soft-cores on FPGA. Experimental results on real hardware show the benefits of the solution, including enabling the seamless launch of virtual machines on different ISAs and extending spatial/temporal isolation to heterogenous cores with enhanced regulation policies.

Cite as

Daniele Ottaviano, Francesco Ciraolo, Renato Mancuso, and Marcello Cinque. The Omnivisor: A Real-Time Static Partitioning Hypervisor Extension for Heterogeneous Core Virtualization over MPSoCs. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 7:1-7:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ottaviano_et_al:LIPIcs.ECRTS.2024.7,
  author =	{Ottaviano, Daniele and Ciraolo, Francesco and Mancuso, Renato and Cinque, Marcello},
  title =	{{The Omnivisor: A Real-Time Static Partitioning Hypervisor Extension for Heterogeneous Core Virtualization over MPSoCs}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{7:1--7:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.7},
  URN =		{urn:nbn:de:0030-drops-203107},
  doi =		{10.4230/LIPIcs.ECRTS.2024.7},
  annote =	{Keywords: Mixed-Criticality, Embedded Virtualization, Real-Time Systems, MPSoCs}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.14

GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks

Authors: Yidi Wang, Cong Liu, Daniel Wong, and Hyoseung Kim

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

Scheduling real-time tasks that utilize GPUs with analyzable guarantees poses a significant challenge due to the intricate interaction between CPU and GPU resources, as well as the complex GPU hardware and software stack. While much research has been conducted in the real-time research community, several limitations persist, including the absence or limited availability of GPU-level preemption, extended blocking times, and/or the need for extensive modifications to program code. In this paper, we propose GCAPS, a GPU Context-Aware Preemptive Scheduling approach for real-time GPU tasks. Our approach exerts control over GPU context scheduling at the device driver level and enables preemption of GPU execution based on task priorities by simply adding one-line macros to GPU segment boundaries. In addition, we provide a comprehensive response time analysis of GPU-using tasks for both our proposed approach as well as the default Nvidia GPU driver scheduling that follows a work-conserving round-robin policy. Through empirical evaluations and case studies, we demonstrate the effectiveness of the proposed approaches in improving taskset schedulability and response time. The results highlight significant improvements over prior work as well as the default scheduling approach, with up to 40% higher schedulability, while also achieving predictable worst-case behavior on Nvidia Jetson embedded platforms.

Cite as

Yidi Wang, Cong Liu, Daniel Wong, and Hyoseung Kim. GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 14:1-14:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wang_et_al:LIPIcs.ECRTS.2024.14,
  author =	{Wang, Yidi and Liu, Cong and Wong, Daniel and Kim, Hyoseung},
  title =	{{GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{14:1--14:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.14},
  URN =		{urn:nbn:de:0030-drops-203170},
  doi =		{10.4230/LIPIcs.ECRTS.2024.14},
  annote =	{Keywords: Real-time systems, GPU scheduling}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.16

Analysis of TSN Time-Aware Shapers Using Schedule Abstraction Graphs

Authors: Srinidhi Srinivasan, Geoffrey Nelissen, Reinder J. Bril, and Nirvana Meratnia

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

IEEE Time-Sensitive Networking (TSN) is one of the main solutions considered by the industry to support time-sensitive communication in data-intensive safety-critical and mission-critical applications such as autonomous driving and smart manufacturing. IEEE TSN standardizes several mechanisms to support real-time traffic on Ethernet networks. Time-Aware Shapers (TAS) (IEEE 802.1Qbv) is the standardized mechanisms of TSN that is usually considered to provide the most deterministic behavior for packet forwarding. TAS regulates when traffic classes may forward incoming packets to the egress of a TSN switch using gates that are opened and closed according to a time-triggered schedule. State-of-the-art solutions to configure or analyze TAS do not allow for multiple traffic classes to have their TAS gates opened at the same time according to any arbitrary schedule. In this paper, we present the first response-time analysis for traffic shaped with TAS where no restriction is enforced on the gate schedule. The proposed analysis is exact. It is a non-trivial variant of the schedule abstraction graph analysis framework [Nasri and Brandenburg, 2017]. Experiments confirm the usefulness of the proposed analysis and show that it is promising for doing design-space exploration where non-conventional TAS gates configurations are investigated to, for instance, improve average-case performance without degrading the worst-case.

Cite as

Srinidhi Srinivasan, Geoffrey Nelissen, Reinder J. Bril, and Nirvana Meratnia. Analysis of TSN Time-Aware Shapers Using Schedule Abstraction Graphs. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 16:1-16:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{srinivasan_et_al:LIPIcs.ECRTS.2024.16,
  author =	{Srinivasan, Srinidhi and Nelissen, Geoffrey and Bril, Reinder J. and Meratnia, Nirvana},
  title =	{{Analysis of TSN Time-Aware Shapers Using Schedule Abstraction Graphs}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{16:1--16:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.16},
  URN =		{urn:nbn:de:0030-drops-203198},
  doi =		{10.4230/LIPIcs.ECRTS.2024.16},
  annote =	{Keywords: TSN, Time-Aware Shapers, TAS, SAG, Schedule Abstraction, latency}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2024.17

Response Time Analysis for Fixed-Priority Preemptive Uniform Multiprocessor Systems

Authors: Binqi Sun, Tomasz Kloda, and Marco Caccamo

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract

We present a response time analysis for global fixed-priority preemptive scheduling of constrained-deadline tasks upon a uniform multiprocessor where each processor can be characterized by a different speed. A fixed-priority scheduler assigns the jobs with the highest priorities to the fastest processors. Since determining whether all tasks can meet their deadlines is generally intractable even with identical processors, we propose two sufficient schedulability tests that calculate upper bounds on the task’s worst-case response time within polynomial and pseudo-polynomial time. The proposed tests leverage the linear programming model to upper bound the interference of the higher-priority tasks. Furthermore, we identify specific conditions and platforms upon which the problem can be solved more efficiently within linear time. These formulations are used to iteratively evaluate and refine possible solutions until a safe upper bound on the task’s worst-case response time is found. Additionally, we demonstrate that, with specific minor modifications, the proposed tests are compatible with Audsley’s optimal priority assignment. Experimental evaluations performed on synthetic task sets show that the proposed approach outperforms the state-of-the-art methods.

Cite as

Binqi Sun, Tomasz Kloda, and Marco Caccamo. Response Time Analysis for Fixed-Priority Preemptive Uniform Multiprocessor Systems. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 17:1-17:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{sun_et_al:LIPIcs.ECRTS.2024.17,
  author =	{Sun, Binqi and Kloda, Tomasz and Caccamo, Marco},
  title =	{{Response Time Analysis for Fixed-Priority Preemptive Uniform Multiprocessor Systems}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{17:1--17:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.17},
  URN =		{urn:nbn:de:0030-drops-203201},
  doi =		{10.4230/LIPIcs.ECRTS.2024.17},
  annote =	{Keywords: Real-time scheduling, Uniform multiprocessor, Response time analysis}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2023.18

Replication-Based Scheduling of Parallel Real-Time Tasks

Authors: Federico Aromolo, Geoffrey Nelissen, and Alessandro Biondi

Published in: LIPIcs, Volume 262, 35th Euromicro Conference on Real-Time Systems (ECRTS 2023)

Abstract

Multiprocessors have become the standard computing platform for real-time embedded systems. To efficiently leverage the computational power of such platforms, software tasks are often characterized by an internal structure where concurrent subtasks can execute in parallel on different processors. Existing strategies for the scheduling of parallel real-time tasks on multiprocessor platforms, such as partitioned, global, and federated scheduling, were inspired by earlier techniques that were not conceived to explicitly support parallel tasks, thus carrying advantages but also well-known limitations. This paper introduces replication-based scheduling, a specialized scheduling paradigm for parallel real-time DAG tasks. Replication-based scheduling leverages the internal structure of the parallel tasks to assign replicas of the subtasks to different processors, while ensuring that exactly one replica of each subtask will be executed at runtime for every task instance. This approach aims at preserving the advantages of partitioned scheduling while simplifying the timing analysis. The replication-based scheduling framework is first defined, together with a strategy for implementing replication-based scheduling in real-time operating systems. Then, offline allocation strategies for subtask replicas and a response-time analysis are presented. In the provided experiments, the schedulability achieved with replication-based scheduling is compared with that of existing techniques for the scheduling of parallel real-time tasks on multiprocessors.

Cite as

Federico Aromolo, Geoffrey Nelissen, and Alessandro Biondi. Replication-Based Scheduling of Parallel Real-Time Tasks. In 35th Euromicro Conference on Real-Time Systems (ECRTS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 262, pp. 18:1-18:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{aromolo_et_al:LIPIcs.ECRTS.2023.18,
  author =	{Aromolo, Federico and Nelissen, Geoffrey and Biondi, Alessandro},
  title =	{{Replication-Based Scheduling of Parallel Real-Time Tasks}},
  booktitle =	{35th Euromicro Conference on Real-Time Systems (ECRTS 2023)},
  pages =	{18:1--18:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-280-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{262},
  editor =	{Papadopoulos, Alessandro V.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2023.18},
  URN =		{urn:nbn:de:0030-drops-180477},
  doi =		{10.4230/LIPIcs.ECRTS.2023.18},
  annote =	{Keywords: Real-Time Systems, Scheduling Algorithms, Schedulability Analysis, Parallel Tasks}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2022.12

Response-Time Analysis for Non-Preemptive Periodic Moldable Gang Tasks

Authors: Geoffrey Nelissen, Joan Marcè i Igual, and Mitra Nasri

Published in: LIPIcs, Volume 231, 34th Euromicro Conference on Real-Time Systems (ECRTS 2022)

Abstract

Gang scheduling has long been adopted by the high-performance computing community as a way to reduce the synchronization overhead between related threads. It allows for several threads to execute in lock steps without suffering from long busy-wait periods or be penalized by large context-switch overheads. When combined with non-preemptive execution, gang scheduling significantly reduces the execution time of threads that work on the same data by decreasing the number of memory transactions required to load or store the data. In this work, we focus on two main types of gang tasks: rigid and moldable. A moldable gang task has a presumed known minimum and maximum number of cores on which it can be executed at runtime, while a rigid gang task always executes on the same number of cores. This work presents the first response-time analysis for non-preemptive moldable gang tasks. Our analysis is based on the notion of schedule abstraction; a new approach for response-time analysis with the promise of high accuracy. Our experiments on periodic rigid gang tasks show that our analysis is 4.9 times more successful in identifying schedulable tasks than the existing utilization-based test for rigid gang tasks.

Cite as

Geoffrey Nelissen, Joan Marcè i Igual, and Mitra Nasri. Response-Time Analysis for Non-Preemptive Periodic Moldable Gang Tasks. In 34th Euromicro Conference on Real-Time Systems (ECRTS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 231, pp. 12:1-12:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{nelissen_et_al:LIPIcs.ECRTS.2022.12,
  author =	{Nelissen, Geoffrey and Marc\`{e} i Igual, Joan and Nasri, Mitra},
  title =	{{Response-Time Analysis for Non-Preemptive Periodic Moldable Gang Tasks}},
  booktitle =	{34th Euromicro Conference on Real-Time Systems (ECRTS 2022)},
  pages =	{12:1--12:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-239-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{231},
  editor =	{Maggio, Martina},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2022.12},
  URN =		{urn:nbn:de:0030-drops-163293},
  doi =		{10.4230/LIPIcs.ECRTS.2022.12},
  annote =	{Keywords: schedulability analysis, response time analysis, moldable gang tasks, rigid gang tasks, schedule abstraction graph, multiprocessor, non-preemptive}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2022.13

Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling

Authors: Federico Aromolo, Alessandro Biondi, and Geoffrey Nelissen

Published in: LIPIcs, Volume 231, 34th Euromicro Conference on Real-Time Systems (ECRTS 2022)

Abstract

The self-suspending task model proved to be particularly effective in capturing the timing behavior of real-time systems characterized by complex execution patterns, such as computation offloading to hardware accelerators, inter-core synchronization by means of multiprocessor locking protocols, and highly parallel computation. Most of the existing results for the timing analysis of self-suspending tasks do not support the widely adopted Earliest Deadline First (EDF) scheduling algorithm, being instead primarily focused on fixed-priority scheduling. This paper presents a response-time analysis for constrained-deadline self-suspending tasks scheduled under EDF on a uniprocessor system. The proposed analysis is based on a model transformation from self-suspending sporadic tasks to sporadic tasks with jitter, which can then be analyzed using a state-of-the-art analysis method for EDF scheduling. Experimental results are presented to compare the performance of the proposed technique in terms of schedulability ratio with that of the pessimistic suspension-oblivious approach and with a less general technique for task sets with implicit deadlines.

Cite as

Federico Aromolo, Alessandro Biondi, and Geoffrey Nelissen. Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling. In 34th Euromicro Conference on Real-Time Systems (ECRTS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 231, pp. 13:1-13:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{aromolo_et_al:LIPIcs.ECRTS.2022.13,
  author =	{Aromolo, Federico and Biondi, Alessandro and Nelissen, Geoffrey},
  title =	{{Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling}},
  booktitle =	{34th Euromicro Conference on Real-Time Systems (ECRTS 2022)},
  pages =	{13:1--13:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-239-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{231},
  editor =	{Maggio, Martina},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2022.13},
  URN =		{urn:nbn:de:0030-drops-163306},
  doi =		{10.4230/LIPIcs.ECRTS.2022.13},
  annote =	{Keywords: Real-Time Systems, Schedulability Analysis, Self-Suspending Tasks, EDF Scheduling}
}

Document

Artifact

DOI: 10.4230/DARTS.8.1.5

Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling (Artifact)

Authors: Federico Aromolo, Alessandro Biondi, and Geoffrey Nelissen

Published in: DARTS, Volume 8, Issue 1, Special Issue of the 34th Euromicro Conference on Real-Time Systems (ECRTS 2022)

Abstract

This artifact provides the means to validate and reproduce the experimental results presented in the related paper "Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling". The paper introduces a response-time analysis for constrained-deadline self-suspending tasks scheduled under EDF on a uniprocessor system, based on a model transformation from self-suspending sporadic tasks to sporadic tasks with jitter. In the experimental evaluation presented in the paper, the performance of the proposed analysis approach for self-suspending tasks is compared with that of existing suspension-oblivious and suspension-aware analysis techniques.

Cite as

Federico Aromolo, Alessandro Biondi, and Geoffrey Nelissen. Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling (Artifact). In Special Issue of the 34th Euromicro Conference on Real-Time Systems (ECRTS 2022). Dagstuhl Artifacts Series (DARTS), Volume 8, Issue 1, pp. 5:1-5:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{aromolo_et_al:DARTS.8.1.5,
  author =	{Aromolo, Federico and Biondi, Alessandro and Nelissen, Geoffrey},
  title =	{{Response-Time Analysis for Self-Suspending Tasks Under EDF Scheduling (Artifact)}},
  pages =	{5:1--5:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2022},
  volume =	{8},
  number =	{1},
  editor =	{Aromolo, Federico and Biondi, Alessandro and Nelissen, Geoffrey},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.8.1.5},
  URN =		{urn:nbn:de:0030-drops-165012},
  doi =		{10.4230/DARTS.8.1.5},
  annote =	{Keywords: Real-Time Systems, Schedulability Analysis, Self-Suspending Tasks, EDF Scheduling}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2021.5

nDimNoC: Real-Time D-dimensional NoC

Authors: Yilian Ribot González, Geoffrey Nelissen, and Eduardo Tovar

Published in: LIPIcs, Volume 196, 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)

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.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

DOI: 10.4230/LIPIcs.ECRTS.2019.21

Response-Time Analysis of Limited-Preemptive Parallel DAG Tasks Under Global Scheduling

Authors: Mitra Nasri, Geoffrey Nelissen, and Björn B. Brandenburg

Published in: LIPIcs, Volume 133, 31st Euromicro Conference on Real-Time Systems (ECRTS 2019)

Abstract

Most recurrent real-time applications can be modeled as a set of sequential code segments (or blocks) that must be (repeatedly) executed in a specific order. This paper provides a schedulability analysis for such systems modeled as a set of parallel DAG tasks executed under any limited-preemptive global job-level fixed priority scheduling policy. More precisely, we derive response-time bounds for a set of jobs subject to precedence constraints, release jitter, and execution-time uncertainty, which enables support for a wide variety of parallel, limited-preemptive execution models (e.g., periodic DAG tasks, transactional tasks, generalized multi-frame tasks, etc.). Our analysis explores the space of all possible schedules using a powerful new state abstraction and state-pruning technique. An empirical evaluation shows the analysis to identify between 10 to 90 percentage points more schedulable task sets than the state-of-the-art schedulability test for limited-preemptive sporadic DAG tasks. It scales to systems of up to 64 cores with 20 DAG tasks. Moreover, while our analysis is almost as accurate as the state-of-the-art exact schedulability test based on model checking (for sequential non-preemptive tasks), it is three orders of magnitude faster and hence capable of analyzing task sets with more than 60 tasks on 8 cores in a few seconds.

Cite as

Mitra Nasri, Geoffrey Nelissen, and Björn B. Brandenburg. Response-Time Analysis of Limited-Preemptive Parallel DAG Tasks Under Global Scheduling. In 31st Euromicro Conference on Real-Time Systems (ECRTS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 133, pp. 21:1-21:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{nasri_et_al:LIPIcs.ECRTS.2019.21,
  author =	{Nasri, Mitra and Nelissen, Geoffrey and Brandenburg, Bj\"{o}rn B.},
  title =	{{Response-Time Analysis of Limited-Preemptive Parallel DAG Tasks Under Global Scheduling}},
  booktitle =	{31st Euromicro Conference on Real-Time Systems (ECRTS 2019)},
  pages =	{21:1--21:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-110-8},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{133},
  editor =	{Quinton, Sophie},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2019.21},
  URN =		{urn:nbn:de:0030-drops-107587},
  doi =		{10.4230/LIPIcs.ECRTS.2019.21},
  annote =	{Keywords: parallel DAG tasks, global multiprocessor scheduling, schedulability analysis, non-preemptive jobs, precedence constraints, worst-case response time, OpenMP}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2018.9

A Response-Time Analysis for Non-Preemptive Job Sets under Global Scheduling

Authors: Mitra Nasri, Geoffrey Nelissen, and Björn B. Brandenburg

Published in: LIPIcs, Volume 106, 30th Euromicro Conference on Real-Time Systems (ECRTS 2018)

Abstract

An effective way to increase the timing predictability of multicore platforms is to use non-preemptive scheduling. It reduces preemption and job migration overheads, avoids intra-core cache interference, and improves the accuracy of worst-case execution time (WCET) estimates. However, existing schedulability tests for global non-preemptive multiprocessor scheduling are pessimistic, especially when applied to periodic workloads. This paper reduces this pessimism by introducing a new type of sufficient schedulability analysis that is based on an exploration of the space of possible schedules using concise abstractions and state-pruning techniques. Specifically, we analyze the schedulability of non-preemptive job sets (with bounded release jitter and execution time variation) scheduled by a global job-level fixed-priority (JLFP) scheduling algorithm upon an identical multicore platform. The analysis yields a lower bound on the best-case response-time (BCRT) and an upper bound on the worst-case response time (WCRT) of the jobs. In an empirical evaluation with randomly generated workloads, we show that the method scales to 30 tasks, a hundred thousand jobs (per hyperperiod), and up to 9 cores.

Cite as

Mitra Nasri, Geoffrey Nelissen, and Björn B. Brandenburg. A Response-Time Analysis for Non-Preemptive Job Sets under Global Scheduling. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 9:1-9:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{nasri_et_al:LIPIcs.ECRTS.2018.9,
  author =	{Nasri, Mitra and Nelissen, Geoffrey and Brandenburg, Bj\"{o}rn B.},
  title =	{{A Response-Time Analysis for Non-Preemptive Job Sets under Global Scheduling}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{9:1--9:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-075-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{106},
  editor =	{Altmeyer, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2018.9},
  URN =		{urn:nbn:de:0030-drops-89941},
  doi =		{10.4230/LIPIcs.ECRTS.2018.9},
  annote =	{Keywords: global multiprocessor scheduling, schedulability analysis, non-preemptive tasks, worst-case response time, best-case response time}
}

Document

DOI: 10.4230/LIPIcs.ECRTS.2018.26

On Strong and Weak Sustainability, with an Application to Self-Suspending Real-Time Tasks

Authors: Felipe Cerqueira, Geoffrey Nelissen, and Björn B. Brandenburg

Published in: LIPIcs, Volume 106, 30th Euromicro Conference on Real-Time Systems (ECRTS 2018)

Abstract

Motivated by an apparent contradiction regarding whether certain scheduling policies are sustainable, we revisit the topic of sustainability in real-time scheduling and argue that the existing definitions of sustainability should be further clarified and generalized. After proposing a formal, generic sustainability theory, we relax the existing notion of (strongly) sustainable scheduling policy to provide a new classification called weak sustainability. Proving weak sustainability properties allows reducing the number of variables that must be considered in the search of a worst-case schedule, and hence enables more efficient schedulability analyses and testing regimes even for policies that are not (strongly) sustainable. As a proof of concept, and to better understand a model for which many mistakes were found in the literature, we study weak sustainability in the context of dynamic self-suspending tasks, where we formalize a generic suspension model using the Coq proof assistant and provide a machine-checked proof that any JLFP scheduling policy is weakly sustainable with respect to job costs and variable suspension times.

Cite as

Felipe Cerqueira, Geoffrey Nelissen, and Björn B. Brandenburg. On Strong and Weak Sustainability, with an Application to Self-Suspending Real-Time Tasks. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 26:1-26:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{cerqueira_et_al:LIPIcs.ECRTS.2018.26,
  author =	{Cerqueira, Felipe and Nelissen, Geoffrey and Brandenburg, Bj\"{o}rn B.},
  title =	{{On Strong and Weak Sustainability, with an Application to Self-Suspending Real-Time Tasks}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{26:1--26:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-075-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{106},
  editor =	{Altmeyer, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2018.26},
  URN =		{urn:nbn:de:0030-drops-89773},
  doi =		{10.4230/LIPIcs.ECRTS.2018.26},
  annote =	{Keywords: real-time scheduling, sustainability, self-suspending tasks, machine-checked proofs}
}

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