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Adaptive Hierarchical Scheduling Framework for Real-Time Systems
Mälardalen University, School of Innovation, Design and Engineering. (Complex Real-time Systems)ORCID iD: 0000-0003-2670-3022
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Modern computer systems are often designed to play a multipurpose role. Therefore, they are capable of running a number of software tasks (software programs) simultaneously in parallel. These software tasks should share the processor such that all of them run and finish their computations as expected. On the other hand, a number of software tasks have timing requirements meaning that they should not only access the processing unit, but this access should also be in a timely manner. Thus, there is a need to timely share the processor among different software programs (applications). The time-sharing often is realized by assigning a fixed and predefined processor time-portion to each application. However, there exists a group of applications where, i) their processor demand is changing in a wide range during run-time, and/or ii) their occasional timing violations can be tolerated. For systems that contain applications with the two aforementioned properties, it is not efficient to assign the applications with fixed processor time-portions. Because, if we allocate the processor resource based on the maximum resource demand of the applications, then the processor's computing capacity will be wasted during the time intervals where the applications will require a smaller portion than maximum resource demand. To this end, in this thesis we propose adaptive processor time-portion assignments. In our adaptive scheme, at each point in time, we monitor the actual demand of the applications, and we provide sufficient processor time-portions for each application. In doing so, we are able to integrate more applications on a shared and resource constrained system, while at the same time providing the applications with timing guarantees.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2013.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 167
National Category
Computer Systems
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-18752ISBN: 978-91-7485-111-3 (print)OAI: oai:DiVA.org:mdh-18752DiVA: diva2:621579
Presentation
2013-06-13, Lambda, Mälardalens högskola, Västerås, 13:30 (English)
Opponent
Supervisors
Available from: 2013-05-16 Created: 2013-04-19 Last updated: 2013-12-03Bibliographically approved
List of papers
1. Towards Adaptive Hierarchical Scheduling of Real-Time Systems
Open this publication in new window or tab >>Towards Adaptive Hierarchical Scheduling of Real-Time Systems
2011 (English)In: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA, 2011 / [ed] Mammeri, Z., New York: IEEE , 2011, 1-8 p.Conference paper, Published paper (Refereed)
Abstract [en]

Hierarchical scheduling provides a modular framework for integrating, scheduling and guaranteeing timing constraints of compositional real-time systems. In such a scheduling framework, all modules should receive a sufficient portion of the shared CPU to be able to guarantee timing constraints of their internal parts. In dynamic systems i.e., systems where the execution time of tasks are subjected to sudden and drastic changes during run-time, assigning fixed CPU portions to the modules is conducive to either low CPU utilization or numerous task deadline misses. In this paper, in order to address this problem, we propose an adaptive CPU allocation method which dynamically assigns CPU portions to the modules during run-time based on their current CPU demand. Besides, the presented approach is evaluated using a series of different simulations. In addition, we present a method for scheduling modules in situations when the CPU resource is not sufficient for scheduling all modules. We introduce the notion of module (subsystem) criticality, and in an overload situation we distribute the CPU resource based on the criticality of modules.

Place, publisher, year, edition, pages
New York: IEEE, 2011
National Category
Computer and Information Science
Identifiers
urn:nbn:se:mdh:diva-13615 (URN)10.1109/ETFA.2011.6059019 (DOI)000297542900046 ()2-s2.0-80655132167 (Scopus ID)978-1-4577-0018-7 (ISBN)
Conference
16th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA) Location: Toulouse, FRANCE Date: SEP 05-09, 2011
Available from: 2011-12-15 Created: 2011-12-15 Last updated: 2013-12-03Bibliographically approved
2. Adaptive Hierarchical Scheduling Framework: Configuration and Evaluation
Open this publication in new window or tab >>Adaptive Hierarchical Scheduling Framework: Configuration and Evaluation
2013 (English)Report (Other academic)
Abstract [en]

We have introduced an adaptive hierarchicalscheduling framework as a solution for composing dynamic realtime systems, i.e., systems where the CPU demand of its tasks aresubjected to unknown and potentially drastic changes during runtime. The framework consists of a controller which periodicallyadapts the system to the current load situation. In this paper,we unveil and explore the detailed behavior and performanceof such an adaptive framework. Specifically, we investigate thecontroller configurations enabling efficient control parameterswhich maximizes performance, and we evaluate the adaptiveframework against a traditional static one.

Place, publisher, year, edition, pages
Västerås: MRTC/Mälardalen University, 2013
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-19011 (URN)
Available from: 2013-05-15 Created: 2013-05-15 Last updated: 2013-12-03Bibliographically approved
3. Bandwidth Adaptation in Hierarchical Scheduling Using Fuzzy Controllers
Open this publication in new window or tab >>Bandwidth Adaptation in Hierarchical Scheduling Using Fuzzy Controllers
2012 (English)In: 7th IEEE International Symposium on Industrial Embedded Systems, SIES 2012 - Conference Proceedings, 2012, 148-157 p.Conference paper, Published paper (Refereed)
Abstract [en]

In our previous work, we have introduced an adaptive hierarchical scheduling framework as a solution for composing dynamic real-time systems, i.e., systems where the CPU demand of their tasks are subjected to unknown and potentially drastic changes during run-time. The framework uses the PI controller which periodically adapts the system to the current load situation. The conventional PI controller despite simplicity and low CPU overhead, provides acceptable performance. However, increasing the pressure on the controller e.g, with an application consisting of multiple tasks with drastically oscillating execution times, degrades the performance of the PI controller. Therefore, in this paper we modify the structure of our adaptive framework by replacing the PI controller with a fuzzy controller to achieve better performance. Furthermore, we conduct a simulation based case study in which we compose dynamic tasks such as video decoder tasks with a set of static tasks into a single system, and we show that the new fuzzy controller outperforms our previous PI controller.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-17266 (URN)10.1109/SIES.2012.6356580 (DOI)2-s2.0-84871577601 (Scopus ID)978-146732684-1 (ISBN)
Conference
7th IEEE International Symposium on Industrial Embedded Systems, SIES 2012; Karlsruhe; 20 June 2012 through 22 June 2012
Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2015-09-24Bibliographically approved
4. Multi-Level Adaptive Hierarchical Scheduling Framework for Composing Real-Time Systems
Open this publication in new window or tab >>Multi-Level Adaptive Hierarchical Scheduling Framework for Composing Real-Time Systems
2013 (English)Report (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-19012 (URN)
Available from: 2013-05-15 Created: 2013-05-15 Last updated: 2013-12-03Bibliographically approved
5. Implementation of the Multi-Level Adaptive Hierarchical Scheduling Framework
Open this publication in new window or tab >>Implementation of the Multi-Level Adaptive Hierarchical Scheduling Framework
2013 (English)Report (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-19013 (URN)
Available from: 2013-05-15 Created: 2013-05-15 Last updated: 2014-01-16Bibliographically approved

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