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Documents authored by Pathan, Risat Mahmud

Document
DOI: 10.4230/LIPIcs.ECRTS.2018.12
Improving the Schedulability and Quality of Service for Federated Scheduling of Parallel Mixed-Criticality Tasks on Multiprocessors

Authors: Risat Mahmud Pathan

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

Abstract
This paper presents federated scheduling algorithm, called MCFQ, for a set of parallel mixed-criticality tasks on multiprocessors. The main feature of MCFQ algorithm is that different alternatives to assign each high-utilization, high-critical task to the processors are computed. Given the different alternatives, we carefully select one alternative for each such task so that all the other tasks can be successfully assigned on the remaining processors. Such flexibility in choosing the right alternative has two benefits. First, it has higher likelihood to satisfy the total resource requirement of all the tasks while ensuring schedulability. Second, computational slack becomes available by intelligently selecting the alternative such that the total resource requirement of all the tasks is minimized. Such slack then can be used to improve the QoS of the system (i.e., never discard some low-critical tasks). Our experimental results using randomly-generated parallel mixed-critical tasksets show that MCFQ can schedule much higher number of tasksets and can improve the QoS of the system significantly in comparison to the state of the art.
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Risat Mahmud Pathan. Improving the Schedulability and Quality of Service for Federated Scheduling of Parallel Mixed-Criticality Tasks on Multiprocessors. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 12:1-12:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{pathan:LIPIcs.ECRTS.2018.12,
  author =	{Pathan, Risat Mahmud},
  title =	{{Improving the Schedulability and Quality of Service for Federated Scheduling of Parallel Mixed-Criticality Tasks on Multiprocessors}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{12:1--12:22},
  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.2018.12},
  URN =		{urn:nbn:de:0030-drops-89915},
  doi =		{10.4230/LIPIcs.ECRTS.2018.12},
  annote =	{Keywords: mixed-criticality systems, real-time systems, multiprocessor scheduling, federated scheduling}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2017.19
Improving the Quality-of-Service for Scheduling Mixed-Criticality Systems on Multiprocessors

Authors: Risat Mahmud Pathan

Published in: LIPIcs, Volume 76, 29th Euromicro Conference on Real-Time Systems (ECRTS 2017)

Abstract
The traditional Vestal's model of Mixed-Criticality (MC) systems was recently extended to Imprecise Mixed-Critical task model (IMC) to guarantee some minimum level of (degraded) service to the low-critical tasks even after the system switches to the high-critical behavior. This paper extends the IMC task model by associating specific Quality-of-Service (QoS) values with the low-critical tasks and proposes a fluid-based scheduling algorithm, called MCFQ, for such task model. The MCFQ algorithm allows some low-critical tasks to provide full service even during the high-critical behavior so that the QoS of the overall system is increased. To the best of our knowledge MCFQ is the first algorithm for IMC task sets considering multiprocessor platform and QoS values. By extending the recently proposed MC-Fluid and MCF fluid-based multiprocessor scheduling algorithms for IMC task model, empirical results show that MCFQ algorithm can significantly improve the QoS of the system in comparison to that of both MC-Fluid and MCF. In addition, the schedulability performance of MCFQ is very close to the optimal MC-Fluid algorithm. Finally, we prove that the MCFQ algorithm has a speedup bound of 4/3, which is optimal for IMC tasks.
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Risat Mahmud Pathan. Improving the Quality-of-Service for Scheduling Mixed-Criticality Systems on Multiprocessors. In 29th Euromicro Conference on Real-Time Systems (ECRTS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 76, pp. 19:1-19:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{pathan:LIPIcs.ECRTS.2017.19,
  author =	{Pathan, Risat Mahmud},
  title =	{{Improving the Quality-of-Service for Scheduling Mixed-Criticality Systems on Multiprocessors}},
  booktitle =	{29th Euromicro Conference on Real-Time Systems (ECRTS 2017)},
  pages =	{19:1--19:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-037-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{76},
  editor =	{Bertogna, Marko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2017.19},
  URN =		{urn:nbn:de:0030-drops-71579},
  doi =		{10.4230/LIPIcs.ECRTS.2017.19},
  annote =	{Keywords: Mixed-Criticality Systems, Real-Time Systems, Multiprocessor Scheduling, Quality of Service, Imprecise Computation}
}
Document
DOI: 10.4230/LITES-v003-i001-a002
Real-Time Scheduling on Uni- and Multiprocessors based on Priority Promotions

Authors: Risat Mahmud Pathan

Published in: LITES, Volume 3, Issue 1 (2016). Leibniz Transactions on Embedded Systems, Volume 3, Issue 1

Abstract
This paper addresses the problem of real-time scheduling of a set of sporadic tasks on uni- and multiprocessor platform based on priority promotion. A new preemptive scheduling algorithm, called Fixed-Priority with Priority Promotion (FPP), is proposed. In FPP scheduling, tasks are executed similar to traditional fixed-priority (FP) scheduling but the priority of some tasks are promoted at fixed time interval (called, promotion point) relative to the release time of each job. A policy called Increase Priority at Deadline Difference (IPDD) to compute the promotion points and promoted priorities for each task is proposed. FPP scheduling prioritizes jobs according to Earliest-Deadline-First (EDF) priority when all tasks' priorities follow IPDD policy.It is known that managing (i.e., inserting and removing) jobs in the ready queue of traditional EDF scheduler is more complex than that of FP scheduler. To avoid such problem in FPP scheduling, a simple data structure and efficient operations to manage jobs in the ready queue are proposed. In addition, techniques for implementing priority promotions with and without the use of a hardware timer are proposed.Finally, an effective scheme to reduce the average number of priority promotions is proposed: if a task set is not schedulable using traditional FP scheduling, then promotion points are assigned only to those tasks that need them to meet the deadlines; otherwise, tasks are assigned traditional fixed priorities without any priority promotion. Empirical investigation shows the effectiveness of the proposed scheme in reducing overhead on uniprocessor and in accepting larger number of task sets in comparison to that of using state-of-the-art global schedulability tests for multiprocessors.
Cite as

Risat Mahmud Pathan. Real-Time Scheduling on Uni- and Multiprocessors based on Priority Promotions. In LITES, Volume 3, Issue 1 (2016). Leibniz Transactions on Embedded Systems, Volume 3, Issue 1, pp. 02:1-02:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@Article{pathan:LITES-v003-i001-a002,
  author =	{Pathan, Risat Mahmud},
  title =	{{Real-Time Scheduling on Uni- and Multiprocessors based on Priority Promotions}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{02:1--02:29},
  ISSN =	{2199-2002},
  year =	{2016},
  volume =	{3},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v003-i001-a002},
  doi =		{10.4230/LITES-v003-i001-a002},
  annote =	{Keywords: Real-Time Systems, Priority Promotion, Schedulability Analysis, Schedulability Condition}
}
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