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Computing the minimum EDF feasible deadline in periodic systems
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
Real-Time Systems Laboratory Scuola Superiore Sant’Anna Pisa, Italy.
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).ORCID iD: 0000-0002-6526-3931
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
2006 (English)In: 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, 2006. Proceedings, Los Alamitos, Calif.: IEEE Press, 2006, p. 125-134Conference paper, Published paper (Refereed)
Abstract [en]

In most real-time applications, deadlines are artifices that need to be enforced to meet different performance requirements. For example, in periodic task sets, jitter requirements can be met by assigning suitable relative deadlines and guaranteeing the feasibility of the schedule. This paper presents a method (called minD) for calculating the minimum EDF-feasible deadline of a real-time task. More precisely, given a set of periodic tasks with hard real-time requirements, which is feasible under EDF, the proposed algorithm allows computing the shortest deadline that can be assigned to an arbitrary task in the set, or to a new incoming task (periodic or aperiodic), still preserving the EDF feasibility of the new task set. The algorithm has a pseudo polynomial complexity and handles arbitrary relative deadlines, which can be less than, equal to, or greater than periods.

Place, publisher, year, edition, pages
Los Alamitos, Calif.: IEEE Press, 2006. p. 125-134
Series
IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, ISSN 1533-2306 ; 2006
Keywords [en]
Real-time, Scheduling
National Category
Computer and Information Sciences
Identifiers
URN: urn:nbn:se:hh:diva-372DOI: 10.1109/RTCSA.2006.22ISI: 000240851900019Scopus ID: 2-s2.0-34547275304Local ID: 2082/696ISBN: 0-7695-2676-4 OAI: oai:DiVA.org:hh-372DiVA, id: diva2:237551
Conference
12th IEEE Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2006), 16-18 August 2006, Sydney, Australia
Note

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Available from: 2007-01-05 Created: 2007-01-05 Last updated: 2018-03-23Bibliographically approved
In thesis
1. Enhancing the Performance of Distributed Real-time Systems
Open this publication in new window or tab >>Enhancing the Performance of Distributed Real-time Systems
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Advanced embedded systems can consist of many sensors, actuators and processors that are deployed on one or several boards, while having a demand of interacting with each other and sharing resources. Communication between different components usually has strict timing constraints. There is thus a strong need to provide solutions for time critical communication. This thesis focuses on both the support of real-time services over standard switched Ethernet networks and the improvement of systems' real-time characteristics, such as reducing delay and jitter in processors and on communication links.

Switched Ethernet has been chosen in this work because of its major advantages in industry; it supports higher bit-rates than most other current LAN (Local Area Network) technologies, including field buses, still at a low cost. We propose using a star network topology with a single Ethernet switch. Each node is connected to a separate port of the switch via a full-duplex link, thereby eliminating collisions. A solid real-time communication protocol for switched Ethernet networks is proposed in the thesis, including a real-time layer between the Ethernet layer and the TCP/IP suite. The network has the capability of supporting both real-time and non real-time traffic and assuring adaptation to the surrounding protocol standards.

Most embedded systems work in a dynamic environment, where the precise behavior of the network traffic can usually not be predicted. To support real-time services, we have chosen the Earliest Deadline scheduling algorithm (EDF) because of its optimality, high efficiency and suitability for being used in adaptive schemes. To be able to increase the amount of guaranteed real-time traffic, the notion of Asymmetric Deadline Partitioning Scheme (ADPS) is introduced. ADPS allows distribution of the end-to-end deadline of a message, sent from any source node in the network to any destination node via the switch, into two sub-deadlines, one for each hop according to the load of the physical link that it must traverse.

For the EDF scheduling algorithm, the feasibility test is one of the most important techniques that provides us with information about whether or not the real-time traffic can be guaranteed by the network. With the same computational complexity as the feasibility test, a method has been developed to compute the minimum EDF-feasible deadline for a real-time task. The importance of this method in real-time applications lies in that it can be effectively used to reduce the response times of specific control activities or limit their input-output jitter. To allow more flexibility in the control of delay and jitter in real-time systems, a general approach for reducing task deadlines according to the requirements of individual tasks has been developed. The method allows the user to specify a deadline reduction factor for each task in order to better exploit the available slack according to the tasks' actual requirements.

Place, publisher, year, edition, pages
Göteborg: Chalmers university of technology, 2007. p. 156
Series
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie, ISSN 0346-718X ; 2599
Keywords
Switched Ethernet, Real-Time Communication, EDF scheduling, Reducation of delay and jitter
National Category
Computer Sciences
Identifiers
urn:nbn:se:hh:diva-1986 (URN)2082/2381 (Local ID)978-91-7291-918-1 (ISBN)2082/2381 (Archive number)2082/2381 (OAI)
Public defence
2007-05-14, Wigforssalen, Halmstad, 10:15 (English)
Opponent
Supervisors
Note

Ingår även i serien: Technical report. D / Department of Computer Science and Engineering, Chalmers University of Technology, 1653-1787 ; 28

Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2018-03-23Bibliographically approved

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Hoang, HoaiJonsson, MagnusKarlsson, Stefan

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