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Towards Hierarchical Scheduling in VxWorks
Mälardalen University, School of Innovation, Design and Engineering. (PROGRESS)ORCID iD: 0000-0002-1687-930X
Mälardalen University, School of Innovation, Design and Engineering. (PROGRESS)ORCID iD: 0000-0001-6132-7945
Mälardalen University, School of Innovation, Design and Engineering.ORCID iD: 0000-0001-6157-5199
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2008 (English)In: OSPERT 2008, Proceedings of the Fourth International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, 2008, p. 63-72Conference paper, Published paper (Refereed)
Abstract [en]

Over the years, we have worked on hierarchical schedulingframeworks from a theoretical point of view. In thispaper we present our initial results of the implementationof our hierarchical scheduling framework in a commercialoperating system VxWorks. The purpose of the implementationis twofold: (1) we would like to demonstrate feasibilityof its implementation in a commercial operating system,without having to modify the kernel source code, and (2) wewould like to present detailed figures of various key propertieswith respect to the overhead of the implementation.During the implementation of the hierarchical scheduler,we have also developed a number of simple task schedulers.We present details of the implementation of Rate-Monotonic(RM) and Earliest Deadline First (EDF) schedulers. Finally,we present the design of our hierarchical schedulingframework, and we discuss our current status in the project.

Place, publisher, year, edition, pages
2008. p. 63-72
National Category
Computer Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-1319OAI: oai:DiVA.org:mdh-1319DiVA, id: diva2:37874
Conference
OSPERT 2008, Fourth International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, Prague, Czech Republic, July 1, 2008
Projects
PROGRESSAvailable from: 2008-10-15 Created: 2008-10-15 Last updated: 2018-01-12Bibliographically approved
In thesis
1. Hierarchical Real Time Scheduling and Synchronization
Open this publication in new window or tab >>Hierarchical Real Time Scheduling and Synchronization
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

 

The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation.

In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism.

In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness

 

 

 

 

 

 

 

Place, publisher, year, edition, pages
Västerås: Mälardalens högskola, 2008. p. 153
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 94
National Category
Computer Engineering
Research subject
Datavetenskap
Identifiers
urn:nbn:se:mdh:diva-1324 (URN)978-91-86135-09-6 (ISBN)
Presentation
Kappa, Västerås (English)
Opponent
Supervisors
Available from: 2008-10-15 Created: 2008-10-15 Last updated: 2018-01-12Bibliographically approved
2. On the Development of Hierarchical Real-Time Systems
Open this publication in new window or tab >>On the Development of Hierarchical Real-Time Systems
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Hierarchical scheduling (also referred to as resource reservation) is a hot topic within the research of real-time systems. It has many advantages such that it can facilitate software integration, fault isolation, structured analysis, legacy system integration etc. The main idea is to partition resources into well defined slots and the resource itself may be the processor, memory etc. This technique is rarely used in real-time applications, however, it is well adopted in the avionics industry in order to isolate error propagation between system parts, and facilitate analysis of the system.Much of the research within resource reservation deals with theoretical schedulability analysis of partitioned systems, including shared resources (other than the processor). We will in this thesis address more practical issues related to resource reservation. We focus on implementation and prototyping aspects, as well as verification and instrumentation. One of our assumptions is that we deal only with fixed-priority preemptive scheduling (FPPS).The first part in this thesis deals with individual software systems that may have its own tasks as well as a scheduler and it is assumed to be part of another larger system, hence, we refer to this individual system as a subsystem. The subsystem is assumed to be integrated together with other subsystems, but at a early stage, we make it possible to simulate the subsystem running together with the rest of the subsystems. This "simulation`` does not require the actual resource reservation mechanism, the only requirement is an operating system with support for FPPS. This pre-study may be a natural step towards the "real`` integration, since each individual subsystem can be test executed within its assigned partition. All subsystems are assumed to run together using a resource reservation mechanism (during the actual integration). We have developed two prototypes of this mechanism. The first prototype is hand-crafted and it is equipped with a program tracer for partitoned based schedulers. This instrumentation is useful for debugging and visualization of program traces for this type of scheduling. The second prototype is developed using timed automata with tasks (task automata). This model-based scheduler is verified for correctness and it is possible to automatically generate source code for the scheduler. We have successfully synthesized this scheduler for the real-time operating system VxWorks. However, it can easily be executed on most other platforms. Both prototypes has pros and cons. The first version has good performance while the second can guarantee its correctness, hence, there is a trade-off between performance and correctness.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2012. p. 154
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 155
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:mdh:diva-14633 (URN)987-91-7485-075-8 (ISBN)
Presentation
2012-06-12, Kappa, Högskoleplan 1, Västerås, 10:15 (English)
Opponent
Supervisors
Available from: 2012-05-21 Created: 2012-05-21 Last updated: 2018-01-12Bibliographically approved

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Behnam, MorisNolte, ThomasÅsberg, MikaelBril, Reinder

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