12 Search Results for "Fisher, Nathan"

Document
DOI: 10.4230/LITES.10.2.2
Improved Elastic Scheduling Algorithms for Implicit-Deadline Tasks

Authors: Marion Sudvarg, Christopher Gill, and Sanjoy Baruah

Published in: LITES, Volume 10, Issue 2 (2025): Special Issue on Industrial Real-Time Systems. Leibniz Transactions on Embedded Systems, Volume 10, Issue 2

Abstract
Elastic scheduling provides a framework under which the utilizations of recurrent tasks are reduced by increasing their periods in response to system overload. The original elastic scheduling model was proposed by Buttazzo et al. in 1998 for implicit-deadline tasks on a uniprocessor and decreases task utilizations to satisfy a schedulable utilization bound. In 2019, Orr and Baruah extended the framework to multiprocessor scheduling of implicit-deadline tasks. In this paper, we propose, analyze, and evaluate new elastic scheduling algorithms for several of the scheduling policies considered in these prior works. In particular, (i) we evaluate an algorithm that we proposed as a short note in the Real-Time Systems journal and demonstrate that it allows for faster admission control than the algorithm of Buttazzo et al. when applied to uniprocessor and fluid scheduling. (ii) We also present faster elastic scheduling algorithms for partitioned EDF scheduling. Finally, (iii) we provide polynomial-time exact elastic scheduling algorithms for global EDF and global RM.
Cite as

Marion Sudvarg, Christopher Gill, and Sanjoy Baruah. Improved Elastic Scheduling Algorithms for Implicit-Deadline Tasks. In LITES, Volume 10, Issue 2 (2025): Special Issue on Industrial Real-Time Systems. Leibniz Transactions on Embedded Systems, Volume 10, Issue 2, pp. 2:1-2:36, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@Article{sudvarg_et_al:LITES.10.2.2,
  author =	{Sudvarg, Marion and Gill, Christopher and Baruah, Sanjoy},
  title =	{{Improved Elastic Scheduling Algorithms for Implicit-Deadline Tasks}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{2:1--2:36},
  ISSN =	{2199-2002},
  year =	{2025},
  volume =	{10},
  number =	{2},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.10.2.2},
  URN =		{urn:nbn:de:0030-drops-252346},
  doi =		{10.4230/LITES.10.2.2},
  annote =	{Keywords: real-time systems, elastic scheduling, scheduling algorithms}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2025.36
Hardness of Finding Kings and Strong Kings

Authors: Ziad Ismaili Alaoui and Nikhil Mande

Published in: LIPIcs, Volume 360, 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)

Abstract
A king in a directed graph is a vertex v such that every other vertex is reachable from v via a path of length at most 2. It is well known that every tournament (a complete graph where each edge has a direction) has at least one king. Our contributions in this work are: - We show that the query complexity of determining existence of a king in arbitrary n-vertex digraphs is Θ(n²). This is in stark contrast to the case where the input is a tournament, where Shen, Sheng, and Wu [SICOMP'03] showed that a king can be found in O(n^{3/2}) queries. - In an attempt to increase the "fairness" in the definition of tournament winners, Ho and Chang [IPL'03] defined a strong king to be a king k such that, for every v that dominates k, the number of length-2 paths from k to v is strictly larger than the number of length-2 paths from v to k. We show that the query complexity of finding a strong king in a tournament is Θ(n²). This answers a question of Biswas, Jayapaul, Raman, and Satti [DAM'22] in the negative. A key component in our proofs is the design of specific tournaments where every vertex is a king, and analyzing certain properties of these tournaments. We feel these constructions and properties are independently interesting and may lead to more interesting results about tournament solutions.
Cite as

Ziad Ismaili Alaoui and Nikhil Mande. Hardness of Finding Kings and Strong Kings. In 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 360, pp. 36:1-36:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{ismailialaoui_et_al:LIPIcs.FSTTCS.2025.36,
  author =	{Ismaili Alaoui, Ziad and Mande, Nikhil},
  title =	{{Hardness of Finding Kings and Strong Kings}},
  booktitle =	{45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)},
  pages =	{36:1--36:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-406-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{360},
  editor =	{Aiswarya, C. and Mehta, Ruta and Roy, Subhajit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2025.36},
  URN =		{urn:nbn:de:0030-drops-250856},
  doi =		{10.4230/LIPIcs.FSTTCS.2025.36},
  annote =	{Keywords: Tournaments, kings, query complexity}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.93
Improved Approximation Algorithms for Capacitated Vehicle Routing with Fixed Capacity

Authors: Jingyang Zhao and Mingyu Xiao

Published in: LIPIcs, Volume 345, 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)

Abstract
The Capacitated Vehicle Routing Problem (CVRP) is one of the most extensively studied problems in combinatorial optimization. Based on customer demand, we distinguish three variants of CVRP: unit-demand, splittable, and unsplittable. In this paper, we consider k-CVRP in general metrics and on general graphs, where k is the vehicle capacity. All three versions are APX-hard for any fixed k ≥ 3. Assume that the approximation ratio of metric TSP is 3/2. We present a (5/2 - Θ(√{1/k}))-approximation algorithm for the splittable and unit-demand cases, and a (5/2 + ln 2 - Θ(√{1/k}))-approximation algorithm for the unsplittable case. Our approximation ratio is better than the previous results when k is less than a sufficiently large value, approximately 1.7 x 10⁷. For small values of k, we design independent and elegant algorithms with further improvements. For the splittable and unit-demand cases, we improve the approximation ratio from 1.792 to 1.500 for k = 3, and from 1.750 to 1.500 for k = 4. For the unsplittable case, we improve the approximation ratio from 1.792 to 1.500 for k = 3, from 2.051 to 1.750 for k = 4, and from 2.249 to 2.157 for k = 5. The approximation ratio for k = 3 surprisingly achieves the same value as in the splittable case. Our techniques, such as EX-ITP - an extension of the classic ITP method, have the potential to improve algorithms for other routing problems as well.
Cite as

Jingyang Zhao and Mingyu Xiao. Improved Approximation Algorithms for Capacitated Vehicle Routing with Fixed Capacity. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 93:1-93:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{zhao_et_al:LIPIcs.MFCS.2025.93,
  author =	{Zhao, Jingyang and Xiao, Mingyu},
  title =	{{Improved Approximation Algorithms for Capacitated Vehicle Routing with Fixed Capacity}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{93:1--93:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-388-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{345},
  editor =	{Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.93},
  URN =		{urn:nbn:de:0030-drops-242008},
  doi =		{10.4230/LIPIcs.MFCS.2025.93},
  annote =	{Keywords: Combinatorial Optimization, Capacitated Vehicle Routing, Approximation Algorithms, Graph Algorithms}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2025.2
Multi-Objective Memory Bandwidth Regulation and Cache Partitioning for Multicore Real-Time Systems

Authors: Binqi Sun, Zhihang Wei, Andrea Bastoni, Debayan Roy, Mirco Theile, Tomasz Kloda, Rodolfo Pellizzoni, and Marco Caccamo

Published in: LIPIcs, Volume 335, 37th Euromicro Conference on Real-Time Systems (ECRTS 2025)

Abstract
Memory bandwidth regulation and cache partitioning are widely used techniques for achieving predictable timing in real-time computing systems. Combined with partitioned scheduling, these methods require careful co-allocation of tasks and resources to cores, as task execution times strongly depend on available allocated resources. To address this challenge, this paper presents a 0-1 linear program for task-resource co-allocation, along with a multi-objective heuristic designed to minimize resource usage while guaranteeing schedulability under a preemptive EDF scheduling policy. Our heuristic employs a multi-layer framework, where an outer layer explores resource allocations using Pareto-pruned search, and an inner layer optimizes task allocation by solving a knapsack problem using dynamic programming. To evaluate the performance of the proposed optimization algorithm, we profile real-world benchmarks on an embedded AMD UltraScale+ ZCU102 platform, with fine-grained resource partitioning enabled by the Jailhouse hypervisor, leveraging cache set partitioning and MemGuard for memory bandwidth regulation. Experiments based on the benchmarking results show that the proposed 0-1 linear program outperforms existing mixed-integer programs by finding more optimal solutions within the same time limit. Moreover, the proposed multi-objective multi-layer heuristic performs consistently better than the state-of-the-art multi-resource-task co-allocation algorithm in terms of schedulability, resource usage, number of non-dominated solutions, and computational efficiency.
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Binqi Sun, Zhihang Wei, Andrea Bastoni, Debayan Roy, Mirco Theile, Tomasz Kloda, Rodolfo Pellizzoni, and Marco Caccamo. Multi-Objective Memory Bandwidth Regulation and Cache Partitioning for Multicore Real-Time Systems. In 37th Euromicro Conference on Real-Time Systems (ECRTS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 335, pp. 2:1-2:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{sun_et_al:LIPIcs.ECRTS.2025.2,
  author =	{Sun, Binqi and Wei, Zhihang and Bastoni, Andrea and Roy, Debayan and Theile, Mirco and Kloda, Tomasz and Pellizzoni, Rodolfo and Caccamo, Marco},
  title =	{{Multi-Objective Memory Bandwidth Regulation and Cache Partitioning for Multicore Real-Time Systems}},
  booktitle =	{37th Euromicro Conference on Real-Time Systems (ECRTS 2025)},
  pages =	{2:1--2:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-377-5},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{335},
  editor =	{Mancuso, Renato},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2025.2},
  URN =		{urn:nbn:de:0030-drops-235807},
  doi =		{10.4230/LIPIcs.ECRTS.2025.2},
  annote =	{Keywords: Multi-objective optimization, memory bandwidth regulation, cache partitioning, partitioned scheduling, real-time systems}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2025.3
Pydrofoil: Accelerating Sail-Based Instruction Set Simulators

Authors: Carl Friedrich Bolz-Tereick, Luke Panayi, Ferdia McKeogh, Tom Spink, and Martin Berger

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract
We present Pydrofoil, a multi-stage compiler that generates instruction set simulators (ISSs) from processor instruction set architectures (ISAs) expressed in the high-level, verification-oriented ISA specification language Sail. Pydrofoil achieves a > 230× speedup over the C-based ISS generated by Sail on our benchmarks, thanks to the following insights. (i) An ISS is effectively an interpreter loop, and tracing just-in-time (JIT) compilers have proven effective at accelerating those, albeit mostly for dynamically typed languages. (ii) ISS workloads are highly atypical, dominated by intensive bit manipulation operations. Conventional compiler optimisations for general-purpose programming languages have limited impact for speeding up such workloads. We develop suitable domain-specific optimisations. (iii) Neither tracing JIT compilers, nor ahead-of-time (AOT) compilation alone, even with domain-specific optimisations, suffice for the generation of performant ISSs. Pydrofoil therefore implements a hybrid approach, pairing an AOT compiler with a tracing JIT built on the meta-tracing PyPy framework. AOT and JIT use domain-specific optimisations. Our benchmarks demonstrate that combining AOT and JIT compilers provides significantly greater performance gains than using either compiler alone.
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Carl Friedrich Bolz-Tereick, Luke Panayi, Ferdia McKeogh, Tom Spink, and Martin Berger. Pydrofoil: Accelerating Sail-Based Instruction Set Simulators. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 3:1-3:31, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bolztereick_et_al:LIPIcs.ECOOP.2025.3,
  author =	{Bolz-Tereick, Carl Friedrich and Panayi, Luke and McKeogh, Ferdia and Spink, Tom and Berger, Martin},
  title =	{{Pydrofoil: Accelerating Sail-Based Instruction Set Simulators}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{3:1--3:31},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.3},
  URN =		{urn:nbn:de:0030-drops-232962},
  doi =		{10.4230/LIPIcs.ECOOP.2025.3},
  annote =	{Keywords: Instruction set architecture, processor, domain-specific language, just-in-time compilation, meta-tracing}
}
Document
DOI: 10.4230/LITES.10.1.3
Limited-Preemption EDF Scheduling for Multi-Phase Secure Tasks

Authors: Benjamin Standaert, Fatima Raadia, Marion Sudvarg, Sanjoy Baruah, Thidapat Chantem, Nathan Fisher, and Christopher Gill

Published in: LITES, Volume 10, Issue 1 (2025). Leibniz Transactions on Embedded Systems, Volume 10, Issue 1

Abstract
Safety-critical embedded systems such as autonomous vehicles typically have only very limited computational capabilities on board that must be carefully managed to provide required enhanced functionalities. As these systems become more complex and inter-connected, some parts may need to be secured to prevent unauthorized access, or isolated to ensure correctness. We propose the multi-phase secure (MPS) task model as a natural extension of the widely used sporadic task model for modeling both the timing and the security (and isolation) requirements for such systems. Under MPS, task phases reflect execution using different security mechanisms which each have associated execution time costs for startup and teardown. We develop corresponding limited-preemption EDF scheduling algorithms and associated pseudo-polynomial schedulability tests for constrained-deadline MPS tasks. In doing so, we provide a correction to a long-standing schedulability condition for EDF under limited-preemption. Evaluation shows that the proposed tests are efficient to compute for bounded utilizations. We empirically demonstrate that the MPS model successfully schedules more task sets compared to non-preemptive approaches.
Cite as

Benjamin Standaert, Fatima Raadia, Marion Sudvarg, Sanjoy Baruah, Thidapat Chantem, Nathan Fisher, and Christopher Gill. Limited-Preemption EDF Scheduling for Multi-Phase Secure Tasks. In LITES, Volume 10, Issue 1 (2025). Leibniz Transactions on Embedded Systems, Volume 10, Issue 1, pp. 3:1-3:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@Article{standaert_et_al:LITES.10.1.3,
  author =	{Standaert, Benjamin and Raadia, Fatima and Sudvarg, Marion and Baruah, Sanjoy and Chantem, Thidapat and Fisher, Nathan and Gill, Christopher},
  title =	{{Limited-Preemption EDF Scheduling for Multi-Phase Secure Tasks}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{3:1--3:27},
  ISSN =	{2199-2002},
  year =	{2025},
  volume =	{10},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.10.1.3},
  URN =		{urn:nbn:de:0030-drops-230799},
  doi =		{10.4230/LITES.10.1.3},
  annote =	{Keywords: real-time systems, limited-preemption scheduling, trusted execution environments}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2025.16
On Fault Tolerant Single-Shot Logical State Preparation and Robust Long-Range Entanglement

Authors: Thiago Bergamaschi and Yunchao Liu

Published in: LIPIcs, Volume 325, 16th Innovations in Theoretical Computer Science Conference (ITCS 2025)

Abstract
Preparing encoded logical states is the first step in a fault-tolerant quantum computation. Standard approaches based on concatenation or repeated measurement incur a significant time overhead. The Raussendorf-Bravyi-Harrington cluster state [Raussendorf et al., 2005] offers an alternative: a single-shot preparation of encoded states of the surface code, by means of a constant depth quantum circuit, followed by a single round of measurement and classical feedforward [Bravyi et al., 2020]. In this work we generalize this approach and prove that single-shot logical state preparation can be achieved for arbitrary quantum LDPC codes. Our proof relies on a minimum-weight decoder and is based on a generalization of Gottesman’s clustering-of-errors argument [Gottesman, 2014]. As an application, we also prove single-shot preparation of the encoded GHZ state in arbitrary quantum LDPC codes. This shows that adaptive noisy constant depth quantum circuits are capable of generating generic robust long-range entanglement.
Cite as

Thiago Bergamaschi and Yunchao Liu. On Fault Tolerant Single-Shot Logical State Preparation and Robust Long-Range Entanglement. In 16th Innovations in Theoretical Computer Science Conference (ITCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 325, pp. 16:1-16:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bergamaschi_et_al:LIPIcs.ITCS.2025.16,
  author =	{Bergamaschi, Thiago and Liu, Yunchao},
  title =	{{On Fault Tolerant Single-Shot Logical State Preparation and Robust Long-Range Entanglement}},
  booktitle =	{16th Innovations in Theoretical Computer Science Conference (ITCS 2025)},
  pages =	{16:1--16:9},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-361-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{325},
  editor =	{Meka, Raghu},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2025.16},
  URN =		{urn:nbn:de:0030-drops-226444},
  doi =		{10.4230/LIPIcs.ITCS.2025.16},
  annote =	{Keywords: Quantum error correction, fault tolerance, single-shot error correction, logical state preparation}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2020.2
CPU Energy-Aware Parallel Real-Time Scheduling

Authors: Abusayeed Saifullah, Sezana Fahmida, Venkata P. Modekurthy, Nathan Fisher, and Zhishan Guo

Published in: LIPIcs, Volume 165, 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)

Abstract
Both energy-efficiency and real-time performance are critical requirements in many embedded systems applications such as self-driving car, robotic system, disaster response, and security/safety control. These systems entail a myriad of real-time tasks, where each task itself is a parallel task that can utilize multiple computing units at the same time. Driven by the increasing demand for parallel tasks, multi-core embedded processors are inevitably evolving to many-core. Existing work on real-time parallel tasks mostly focused on real-time scheduling without addressing energy consumption. In this paper, we address hard real-time scheduling of parallel tasks while minimizing their CPU energy consumption on multicore embedded systems. Each task is represented as a directed acyclic graph (DAG) with nodes indicating different threads of execution and edges indicating their dependencies. Our technique is to determine the execution speeds of the nodes of the DAGs to minimize the overall energy consumption while meeting all task deadlines. It incorporates a frequency optimization engine and the dynamic voltage and frequency scaling (DVFS) scheme into the classical real-time scheduling policies (both federated and global) and makes them energy-aware. The contributions of this paper thus include the first energy-aware online federated scheduling and also the first energy-aware global scheduling of DAGs. Evaluation using synthetic workload through simulation shows that our energy-aware real-time scheduling policies can achieve up to 68% energy-saving compared to classical (energy-unaware) policies. We have also performed a proof of concept system evaluation using physical hardware demonstrating the energy efficiency through our proposed approach.
Cite as

Abusayeed Saifullah, Sezana Fahmida, Venkata P. Modekurthy, Nathan Fisher, and Zhishan Guo. CPU Energy-Aware Parallel Real-Time Scheduling. In 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 165, pp. 2:1-2:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{saifullah_et_al:LIPIcs.ECRTS.2020.2,
  author =	{Saifullah, Abusayeed and Fahmida, Sezana and Modekurthy, Venkata P. and Fisher, Nathan and Guo, Zhishan},
  title =	{{CPU Energy-Aware Parallel Real-Time Scheduling}},
  booktitle =	{32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)},
  pages =	{2:1--2:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-152-8},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{165},
  editor =	{V\"{o}lp, Marcus},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2020.2},
  URN =		{urn:nbn:de:0030-drops-123655},
  doi =		{10.4230/LIPIcs.ECRTS.2020.2},
  annote =	{Keywords: Real-time scheduling, multicore, energy-efficiency, embedded systems}
}
Document
Artifact
DOI: 10.4230/DARTS.5.1.2
NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling (Artifact)

Authors: Corey Tessler and Nathan Fisher

Published in: DARTS, Volume 5, Issue 1, Special Issue of the 31st Euromicro Conference on Real-Time Systems (ECRTS 2019)

Abstract
The BUNDLE and BUNDLEP scheduling algorithms are cache-cognizant thread-level scheduling algorithms and associated worst case execution time and cache overhead (WCETO) techniques for hard real-time multi-threaded tasks. The BUNDLE-based approaches utilize the inter-thread cache benefit to reduce WCETO values for jobs. Currently, the BUNDLE-based approaches are limited to scheduling a single task. This work aims to expand the applicability of BUNDLE-based scheduling to multiple task multi-threaded task sets. BUNDLE-based scheduling leverages knowledge of potential cache conflicts to selectively preempt one thread in favor of another from the same job. This thread-level preemption is a requirement for the run-time behavior and WCETO calculation to receive the benefit of BUNDLE-based approaches. This work proposes scheduling BUNDLE-based jobs non-preemptively according to the earliest deadline first (EDF) policy. Jobs are forbidden from preempting one another, while threads within a job are allowed to preempt other threads. An accompanying schedulability test is provided, named Threads Per Job (TPJ). TPJ is a novel schedulability test, input is a task set specification which may be transformed (under certain restrictions); dividing threads among tasks in an effort to find a feasible task set. Enhanced by the flexibility to transform task sets and taking advantage of the inter-thread cache benefit, the evaluation shows TPJ scheduling task sets fully preemptive EDF cannot.
Cite as

Corey Tessler and Nathan Fisher. NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling (Artifact). In Special Issue of the 31st Euromicro Conference on Real-Time Systems (ECRTS 2019). Dagstuhl Artifacts Series (DARTS), Volume 5, Issue 1, pp. 2:1-2:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@Article{tessler_et_al:DARTS.5.1.2,
  author =	{Tessler, Corey and Fisher, Nathan},
  title =	{{NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling}},
  pages =	{2:1--2:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2019},
  volume =	{5},
  number =	{1},
  editor =	{Tessler, Corey and Fisher, Nathan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.5.1.2},
  URN =		{urn:nbn:de:0030-drops-107306},
  doi =		{10.4230/DARTS.5.1.2},
  annote =	{Keywords: Scheduling algorithms, Cache Memory, Multi-threading, Static Analysis}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2019.15
NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling

Authors: Corey Tessler and Nathan Fisher

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

Abstract
The BUNDLE and BUNDLEP scheduling algorithms are cache-cognizant thread-level scheduling algorithms and associated worst case execution time and cache overhead (WCETO) techniques for hard real-time multi-threaded tasks. The BUNDLE-based approaches utilize the inter-thread cache benefit to reduce WCETO values for jobs. Currently, the BUNDLE-based approaches are limited to scheduling a single task. This work aims to expand the applicability of BUNDLE-based scheduling to multiple task multi-threaded task sets. BUNDLE-based scheduling leverages knowledge of potential cache conflicts to selectively preempt one thread in favor of another from the same job. This thread-level preemption is a requirement for the run-time behavior and WCETO calculation to receive the benefit of BUNDLE-based approaches. This work proposes scheduling BUNDLE-based jobs non-preemptively according to the earliest deadline first (EDF) policy. Jobs are forbidden from preempting one another, while threads within a job are allowed to preempt other threads. An accompanying schedulability test is provided, named Threads Per Job (TPJ). TPJ is a novel schedulability test, input is a task set specification which may be transformed (under certain restrictions); dividing threads among tasks in an effort to find a feasible task set. Enhanced by the flexibility to transform task sets and taking advantage of the inter-thread cache benefit, the evaluation shows TPJ scheduling task sets fully preemptive EDF cannot.
Cite as

Corey Tessler and Nathan Fisher. NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling. In 31st Euromicro Conference on Real-Time Systems (ECRTS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 133, pp. 15:1-15:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{tessler_et_al:LIPIcs.ECRTS.2019.15,
  author =	{Tessler, Corey and Fisher, Nathan},
  title =	{{NPM-BUNDLE: Non-Preemptive Multitask Scheduling for Jobs with BUNDLE-Based Thread-Level Scheduling}},
  booktitle =	{31st Euromicro Conference on Real-Time Systems (ECRTS 2019)},
  pages =	{15:1--15:23},
  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.2019.15},
  URN =		{urn:nbn:de:0030-drops-107521},
  doi =		{10.4230/LIPIcs.ECRTS.2019.15},
  annote =	{Keywords: Scheduling algorithms, Cache Memory, Multi-threading, Static Analysis}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2019.20
Fast and Effective Multiframe-Task Parameter Assignment Via Concave Approximations of Demand

Authors: Bo Peng, Nathan Fisher, and Thidapat Chantem

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

Abstract
Task parameters in traditional models, e.g., the generalized multiframe (GMF) model, are fixed after task specification time. When tasks whose parameters can be assigned within a range, such as the frame parameters in self-suspending tasks and end-to-end tasks, the optimal offline assignment towards schedulability of such parameters becomes important. The GMF-PA (GMF with parameter adaptation) model proposed in recent work allows frame parameters to be flexibly chosen (offline) in arbitrary-deadline systems. Based on the GMF-PA model, a mixed-integer linear programming (MILP)-based schedulability test was previously given under EDF scheduling for a given assignment of frame parameters in uniprocessor systems. Due to the NP-hardness of the MILP, we present a pseudo-polynomial linear programming (LP)-based heuristic algorithm guided by a concave approximation algorithm to achieve a feasible parameter assignment at a fraction of the time overhead of the MILP-based approach. The concave programming approximation algorithm closely approximates the MILP algorithm, and we prove its speed-up factor is (1+delta)^2 where delta > 0 can be arbitrarily small, with respect to the exact schedulability test of GMF-PA tasks under EDF. Extensive experiments involving self-suspending tasks (an application of the GMF-PA model) reveal that the schedulability ratio is significantly improved compared to other previously proposed polynomial-time approaches in medium and moderately highly loaded systems.
Cite as

Bo Peng, Nathan Fisher, and Thidapat Chantem. Fast and Effective Multiframe-Task Parameter Assignment Via Concave Approximations of Demand. In 31st Euromicro Conference on Real-Time Systems (ECRTS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 133, pp. 20:1-20:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{peng_et_al:LIPIcs.ECRTS.2019.20,
  author =	{Peng, Bo and Fisher, Nathan and Chantem, Thidapat},
  title =	{{Fast and Effective Multiframe-Task Parameter Assignment Via Concave Approximations of Demand}},
  booktitle =	{31st Euromicro Conference on Real-Time Systems (ECRTS 2019)},
  pages =	{20:1--20:22},
  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.2019.20},
  URN =		{urn:nbn:de:0030-drops-107578},
  doi =		{10.4230/LIPIcs.ECRTS.2019.20},
  annote =	{Keywords: generalized multiframe task model (GMF), generalized multiframe task model with parameter adaptation (GMF-PA), self-suspending tasks, uniprocessor scheduling, mixed-integer linear programming, concave approximation, linear programming}
}
Document
DOI: 10.4230/DagSemProc.10071.9
Power-Aware Real-Time Scheduling: Models, Open Problems, and Practical Considerations

Authors: Nathan Fisher

Published in: Dagstuhl Seminar Proceedings, Volume 10071, Scheduling (2010)

Abstract
Power-related issues have received considerable research attention from the real-time community in the past decade. In our talk, we introduce a recent model and set of assumptions made in the recent real-time literature on energy and thermal issues; suggest two high-level open problems for power-aware real-time scheduling: {em peak-temperature minimization} and {em energy-minimization with temperature as a constraint}; and discuss practical considerations that should be considered in proposed solutions.
Cite as

Nathan Fisher. Power-Aware Real-Time Scheduling: Models, Open Problems, and Practical Considerations. In Scheduling. Dagstuhl Seminar Proceedings, Volume 10071, pp. 1-4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{fisher:DagSemProc.10071.9,
  author =	{Fisher, Nathan},
  title =	{{Power-Aware Real-Time Scheduling: Models, Open Problems, and Practical Considerations}},
  booktitle =	{Scheduling},
  pages =	{1--4},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2010},
  volume =	{10071},
  editor =	{Susanne Albers and Sanjoy K. Baruah and Rolf H. M\"{o}hring and Kirk Pruhs},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.10071.9},
  URN =		{urn:nbn:de:0030-drops-25395},
  doi =		{10.4230/DagSemProc.10071.9},
  annote =	{Keywords: Real-time scheduling, power-aware scheduling, sporadic tasks}
}
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