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Prototyping and Code Synthesis of Hierarchically Scheduled Systems using TIMES
Mälardalen University, School of Innovation, Design and Engineering. (Complex Real-Time Embedded Systems (CORE) research group)ORCID iD: 0000-0001-6157-5199
Mälardalen University, School of Innovation, Design and Engineering. (Complex Real-Time Embedded Systems (CORE) research group)ORCID iD: 0000-0001-6132-7945
Mälardalen University, School of Innovation, Design and Engineering.ORCID iD: 0000-0003-4040-3480
2010 (English)In: FTRA Journal of Convergence, ISSN 2093-7741, Vol. 1, no 1, p. 75-84Article in journal (Refereed) Published
Abstract [en]

In hierarchical scheduling a system is organized as a tree of nodes, where each node schedules its child nodes. A node contains tasks and/or subsystems, where a subsystem is typically developed by a development team. Given a system where each part is subcontracted to different developers, they can benefit from hierarchical scheduling by parallel development and simplified integration of subsystems. Each team should have the possibility to test their system before integration. Hence, we show how a node, in a hierarchical scheduling tree, can be analyzed in the Times tool by replacing all interference from nodes with a small set of higher priority tasks. We show an algorithm that can generate these tasks, including their parameters. Further, we use the Times code-generator, in combination with operating system extensions, to generate source code that emulates the scheduling environment for a subsystem, in an arbitrary level in the tree. Our experiments include two example systems. In the first case we generate source code for an industrial oriented platform (VxWorks) and conduct a performance evaluation. In the second example we generate source code that emulates the scheduling environment for a video application, running in Linux, and we perform a frame-rate evaluation.

Place, publisher, year, edition, pages
Seoul, 2010. Vol. 1, no 1, p. 75-84
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-14630OAI: oai:DiVA.org:mdh-14630DiVA, id: diva2:527445
Available from: 2012-05-21 Created: 2012-05-21 Last updated: 2018-01-12Bibliographically approved
In thesis
1. 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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Åsberg, MikaelNolte, ThomasPettersson, Paul

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