4 Search Results for "West, Richard"

Document
DOI: 10.4230/LIPIcs.ECRTS.2020.3
PAStime: Progress-Aware Scheduling for Time-Critical Computing

Authors: Soham Sinha, Richard West, and Ahmad Golchin

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

Abstract
Over-estimation of worst-case execution times (WCETs) of real-time tasks leads to poor resource utilization. In a mixed-criticality system (MCS), the over-provisioning of CPU time to accommodate the WCETs of highly critical tasks may lead to degraded service for less critical tasks. In this paper we present PAStime, a novel approach to monitor and adapt the runtime progress of highly time-critical applications, to allow for improved service to lower criticality tasks. In PAStime, CPU time is allocated to time-critical tasks according to the delays they experience as they progress through their control flow graphs. This ensures that as much time as possible is made available to improve the Quality-of-Service of less critical tasks, while high-criticality tasks are compensated after their delays. This paper describes the integration of PAStime with Adaptive Mixed-criticality (AMC) scheduling. The LO-mode budget of a high-criticality task is adjusted according to the delay observed at execution checkpoints. This is the first implementation of AMC in the scheduling framework of LITMUS^RT, which is extended with our PAStime runtime policy and tested with real-time Linux applications such as object classification and detection. We observe in our experimental evaluation that AMC-PAStime significantly improves the utilization of the low-criticality tasks while guaranteeing service to high-criticality tasks.
Cite as

Soham Sinha, Richard West, and Ahmad Golchin. PAStime: Progress-Aware Scheduling for Time-Critical Computing. In 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 165, pp. 3:1-3:24, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2020)

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@InProceedings{sinha_et_al:LIPIcs.ECRTS.2020.3,
  author =	{Sinha, Soham and West, Richard and Golchin, Ahmad},
  title =	{{PAStime: Progress-Aware Scheduling for Time-Critical Computing}},
  booktitle =	{32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)},
  pages =	{3:1--3:24},
  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.2020.3},
  URN =		{urn:nbn:de:0030-drops-123668},
  doi =		{10.4230/LIPIcs.ECRTS.2020.3},
  annote =	{Keywords: progress-aware scheduling, code instrumentation, timing annotation}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2020.24
smARTflight: An Environmentally-Aware Adaptive Real-Time Flight Management System

Authors: Anam Farrukh and Richard West

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

Abstract
Multi-rotor drones require real-time sensor data processing and control to maintain flight stability, which is made more challenging by external disturbances such as wind. In this paper we introduce smARTflight: an environmentally-aware adaptive real-time flight management system. smARTflight adapts the execution frequencies of flight control tasks according to timing and safety-critical constraints, in response to transient fluctuations of a drone’s attitude. In contrast to current state-of-the-art methods, smARTflight’s criticality-aware scheduler reduces the latency to return to a steady-state target attitude. The system also improves the overall control accuracy and lowers the frequency of adjustments to motor speeds to conserve power. A comparative case-study with a well-known autopilot shows that smARTflight reduces unnecessary control loop executions under stable conditions, while reducing response time latency by as much as 60% in a given axis of rotation when subjected to a 15° step attitude disturbance.
Cite as

Anam Farrukh and Richard West. smARTflight: An Environmentally-Aware Adaptive Real-Time Flight Management System. In 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 165, pp. 24:1-24:22, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2020)

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@InProceedings{farrukh_et_al:LIPIcs.ECRTS.2020.24,
  author =	{Farrukh, Anam and West, Richard},
  title =	{{smARTflight: An Environmentally-Aware Adaptive Real-Time Flight Management System}},
  booktitle =	{32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)},
  pages =	{24:1--24:22},
  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.2020.24},
  URN =		{urn:nbn:de:0030-drops-123874},
  doi =		{10.4230/LIPIcs.ECRTS.2020.24},
  annote =	{Keywords: adaptive real-time systems, safety criticality, flight controller, multi-rotor drones, environmental awareness}
}
Document
DOI: 10.4230/LITES-v004-i001-a002
Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results

Authors: Florian Kluge

Published in: LITES, Volume 4, Issue 1 (2017). Leibniz Transactions on Embedded Systems, Volume 4, Issue 1

Abstract
The concept of a firm real-time task implies the notion of a firm deadline that should not be missed by the jobs of this task. If a deadline miss occurs, the concerned job yields no value to the system. For some applications domains, this restrictive notion can be relaxed. For example, robust control systems can tolerate that single executions of a control loop miss their deadlines, and still yield an acceptable behaviour. Thus, systems can be developed under more optimistic assumptions, e.g. by allowing overloads. However, care must be taken that deadline misses do not accumulate. This restriction can be expressed by the model of (m,k)-firm real-time tasks that require that from any k consecutive jobs at least m are executed successfully. In this article, we extend our prior work on the MKU scheduling heuristic. MKU uses history-cognisant utility functions as means for making decisions in overload situations. We present new theoretical results on MKU and on other schedulers for (m,k)-firm real-time tasks. Based on extensive simulations, we assess the performance of these schedulers. The results allow us to identify task set characteristics that can be used as guidelines for choosing a scheduler for a concrete use case.
Cite as

Florian Kluge. Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results. In LITES, Volume 4, Issue 1 (2017). Leibniz Transactions on Embedded Systems, Volume 4, Issue 1, pp. 02:1-02:25, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)

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@Article{kluge:LITES-v004-i001-a002,
  author =	{Kluge, Florian},
  title =	{{Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results}},
  booktitle =	{LITES, Volume 4, Issue 1 (2017)},
  pages =	{02:1--02:25},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2017},
  volume =	{4},
  number =	{1},
  editor =	{Kluge, Florian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v004-i001-a002},
  doi =		{10.4230/LITES-v004-i001-a002},
  annote =	{Keywords: Real-time Scheduling, (m, k)-Firm Real-Time Tasks}
}
Document
DOI: 10.4230/LITES-v001-i002-a001
Blocking Optimality in Distributed Real-Time Locking Protocols

Authors: Björn Bernhard Brandenburg

Published in: LITES, Volume 1, Issue 2 (2014). Leibniz Transactions on Embedded Systems, Volume 1, Issue 2

Abstract
Lower and upper bounds on the maximum priority inversion blocking (pi-blocking) that is generally unavoidable in distributed multiprocessor real-time locking protocols (where resources may be accessed only from specific synchronization processors) are established. Prior work on suspension-based shared-memory multiprocessor locking protocols (which require resources to be accessible from all processors) has established asymptotically tight bounds of Ω(m) and Ω(n) maximum pi-blocking under suspension-oblivious and suspension-aware analysis, respectively, where m denotes the total number of processors and n denotes the number of tasks. In this paper, it is shown that, in the case of distributed semaphore protocols, there exist two different task allocation scenarios that give rise to distinct lower bounds. In the case of co-hosted task allocation, where application tasks may also be assigned to synchronization processors (i.e., processors hosting critical sections), Ω(Φ · n) maximum pi-blocking is unavoidable for some tasks under any locking protocol under both suspension-aware and suspension-oblivious schedulability analysis, where Φ denotes the ratio of the maximum response time to the shortest period. In contrast, in the case of disjoint task allocation (i.e., if application tasks may not be assigned to synchronization processors), only Ω(m) and Ω(n) maximum pi-blocking is fundamentally unavoidable under suspension-oblivious and suspension-aware analysis, respectively, as in the shared-memory case. These bounds are shown to be asymptotically tight with the construction of two new distributed real-time locking protocols that ensure O(m) and O(n) maximum pi-blocking under suspension-oblivious and suspension-aware analysis, respectively.
Cite as

Björn Bernhard Brandenburg. Blocking Optimality in Distributed Real-Time Locking Protocols. In LITES, Volume 1, Issue 2 (2014). Leibniz Transactions on Embedded Systems, Volume 1, Issue 2, pp. 01:1-01:22, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2014)

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@Article{brandenburg:LITES-v001-i002-a001,
  author =	{Brandenburg, Bj\"{o}rn Bernhard},
  title =	{{Blocking Optimality in Distributed Real-Time Locking Protocols}},
  booktitle =	{LITES, Volume 1, Issue 2 (2014)},
  pages =	{01:1--01:22},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2014},
  volume =	{1},
  number =	{2},
  editor =	{Brandenburg, Bj\"{o}rn Bernhard},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v001-i002-a001},
  doi =		{10.4230/LITES-v001-i002-a001},
  annote =	{Keywords: Distributed multiprocessor real-time systems, Real-time locking, Priority inversion, Blocking optimality}
}
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