Scheduling for embedded real-time systems
TL;DR: The authors review several approaches to control-oriented and dataflow-oriented software scheduling to determine whether a given technique can satisfy deadlines, throughput, and other constraints for embedded real-time systems.
Abstract: The authors review several approaches to control-oriented and dataflow-oriented software scheduling to determine whether a given technique can satisfy deadlines, throughput, and other constraints for embedded real-time systems.
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Book•
01 Jan 2003
TL;DR: Embedded System Design can be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers.
Abstract: Until the late eighties, information processing was associated with large mainframe computers and huge tape drives. During the nineties, this trend shifted towards information processing with personal computers, or PCs. The trend towards miniaturization continues. In the future, most of the information processing systems will be quite small and embedded into larger products such as transportation and fabrication equipment. Hence, these kinds of systems are called embedded systems. It is expected that the total market volume of embedded systems will be significantly larger than that of traditional information processing systems such as PCs and mainframes. Embedded systems share a number of common characteristics. For example, they must be dependable, efficient, meet real-time constraints and require customized user interfaces (instead of generic keyboard and mouse interfaces). Therefore, it makes sense to consider common principles of embedded system design. Embedded System Design starts with an introduction into the area and a survey of specification languages for embedded systems.A brief overview is provided of hardware devices used for embedded systems and also presents the essentials of software design for embedded systems. Real-time operating systems and real-time scheduling are covered briefly.Techniques for implementing embedded systems are also discussed, using hardware/software codesign. It closes with a survey on validation techniques. Embedded System Designcan be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers. The book assumes a basic knowledge of information processing hardware and software.
390 citations
06 Sep 2003
TL;DR: The design and main features of Times are presented including a summary of theoretical results behind the tool and a model checker e.g. UPPAAL is presented.
Abstract: Times is a tool suite designed mainly for symbolic schedulability analysis and synthesis of executable code with predictable behaviours for real-time systems. Given a system design model consisting of (1) a set of application tasks whose executions may be required to meet mixed timing, precedence, and resource constraints, (2) a network of timed automata describing the task arrival patterns and (3) a preemptive or non-preemptive scheduling policy, Times will generate a scheduler, and calculate the worst case response times for the tasks. The design model may be further validated using a model checker e.g. UPPAAL and then compiled to executable C-code using the Times compiler. In this paper, we present the design and main features of Times including a summary of theoretical results behind the tool. Times can be downloaded at www.timestool.com.
230 citations
Cites methods from "Scheduling for embedded real-time s..."
...In Times, we use cyclic AND/OR-precedence graphs in which we distinguish ordinary and inter-iterative edges (denoted 9 9 K) [3] such that inter-iterative precedence constraints apply to all task instances except for the rst one....
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Book•
03 Dec 2010
TL;DR: Embedded System Design can be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers.
Abstract: Until the late 1980s, information processing was associated with large mainframe computers and huge tape drives. During the 1990s, this trend shifted toward information processing with personal computers, or PCs. The trend toward miniaturization continues and in the future the majority of information processing systems will be small mobile computers, many of which will be embedded into larger products and interfaced to the physical environment. Hence, these kinds of systems are called embedded systems. Embedded systems together with their physical environment are called cyber-physical systems. Examples include systems such as transportation and fabrication equipment. It is expected that the total market volume of embedded systems will be significantly larger than that of traditional information processing systems such as PCs and mainframes. Embedded systems share a number of common characteristics. For example, they must be dependable, efficient, meet real-time constraints and require customized user interfaces (instead of generic keyboard and mouse interfaces). Therefore, it makes sense to consider common principles of embedded system design.Embedded System Design starts with an introduction into the area and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, like real-time operating systems. The book also discusses evaluation and validation techniques for embedded systems. Furthermore, the book presents an overview of techniques for mapping applications to execution platforms. Due to the importance of resource efficiency, the book also contains a selected set of optimization techniques for embedded systems, including special compilation techniques. The book closes with a brief survey on testing.Embedded System Design can be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers. It assumes a basic knowledge of information processing hardware and software. Courseware related to this book is available at http://ls12-www.cs.tu-dortmund.de/~marwedel.
213 citations
01 Mar 1999
TL;DR: A new optimization heuristic able to support heterogeneous architectures and takes into account accurately inter-processor communications, which are usually neglected but may reduce dramatically multiprocessor performances.
Abstract: This paper presents an enhancement of our "Algorithm Architecture Adequation" (AAA) prototyping methodology which allows to rapidly develop and optimize the implementation of a reactive real-time dataflow algorithm on a embedded heterogeneous multiprocessor architecture, predict its real-time behavior and automatically generate the corresponding distributed and optimized static executive. It describes a new optimization heuristic able to support heterogeneous architectures and takes into account accurately inter-processor communications, which are usually neglected but may reduce dramatically multiprocessor performances.
182 citations
Cites background from "Scheduling for embedded real-time s..."
...But the price to be paid is the induced overhead [3, 1, 17] both in program size and in execution time (mainly caused by expensive context switching and dynamic communication routing)....
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...On the other hand, static scheduling minimizes the overall execution time by drastically reducing overheads [3, 7], but it does not allow to implement as various application as the dynamic policy does, because all the properties of the application, including its environment, must be known at compile time....
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TL;DR: The goal is to derive a worst case delay by which the system completes execution, such that this delay is as small as possible; to generate a logically and temporally deterministic schedule; and to optimize parameters of the communication protocol such thatThis delay is guaranteed.
Abstract: In this paper, we concentrate on aspects related to the synthesis of distributed embedded systems consisting of programmable processors and application-specific hardware components. The approach is based on an abstract graph representation that captures, at process level, both dataflow and the flow of control. Our goal is to derive a worst case delay by which the system completes execution, such that this delay is as small as possible; to generate a logically and temporally deterministic schedule; and to optimize parameters of the communication protocol such that this delay is guaranteed. We have further investigated the impact of particular communication infrastructures and protocols on the overall performance and, specially, how the requirements of such an infrastructure have to be considered for process and communication scheduling. Not only do particularities of the underlying architecture have to be considered during scheduling but also the parameters of the communication protocol should be adapted to fit the particular embedded application. The optimization algorithm, which implies both process scheduling and optimization of the parameters related to the communication protocol, generates an efficient bus access scheme as well as the schedule tables for activation of processes and communications.
145 citations
Cites background from "Scheduling for embedded real-time s..."
...The approach has been later extended to accommodate more general computational models and has also been applied to distributed systems [18]....
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References
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Book•
03 Jan 1989
TL;DR: In this paper, the problem of multiprogram scheduling on a single processor is studied from the viewpoint of the characteristics peculiar to the program functions that need guaranteed service, and it is shown that an optimum fixed priority scheduler possesses an upper bound to processor utilization which may be as low as 70 percent for large task sets.
Abstract: The problem of multiprogram scheduling on a single processor is studied from the viewpoint of the characteristics peculiar to the program functions that need guaranteed service. It is shown that an optimum fixed priority scheduler possesses an upper bound to processor utilization which may be as low as 70 percent for large task sets. It is also shown that full processor utilization can be achieved by dynamically assigning priorities on the basis of their current deadlines. A combination of these two scheduling techniques is also discussed.
5,397 citations
TL;DR: The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher and the predictions that follow are seen to be in close agreement with the behaviour exhibited during simulation studies.
Abstract: The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher. The tasks to be scheduled are allowed to experience internal blocking (from other tasks with which they share resources) and (with certain restrictions) to release jitter, such as waiting for a message to arrive. The analysis presented is more general than that previously published and subsumes, for example, techniques based on the Rate Monotonic approach. In addition to presenting the relevant theory, an existing avionics case study is described and analysed. The predictions that follow from this analysis are seen to be in close agreement with the behaviour exhibited during simulation studies.
1,168 citations
TL;DR: The software engineering baccalaureate program consists of a rigorous curriculum of science, math, computer science, and software engineering courses.
Abstract: Software engineers work on multidisciplinary teams to identify and develop software solutions and to maintain software intensive systems of all sizes. The focus of this program is on the rigorous engineering practices necessary to build, maintain, and protect modern software intensive systems. Consistent with this focus, the software engineering baccalaureate program consists of a rigorous curriculum of science, math, computer science, and software engineering courses.
1,124 citations
TL;DR: Ptolemy as discussed by the authors is an environment for simulation and prototyping of heterogeneous systems, which uses object-oriented software technology to model each subsystem in a natural and efficient manner, and to integrate these subsystems into a whole.
Abstract: Ptolemy is an environment for simulation and prototyping of heterogeneous systems. It uses modern object-oriented software technology (C++) to model each subsystem in a natural and efficient manner, and to integrate these subsystems into a whole. Ptolemy encompasses practically all aspects of designing signal processing and communications systems, ranging from algorithms and communication strategies, simulation, hardware and software design, parallel computing, and generating real-time prototypes. To accommodate this breadth, Ptoloemy must support a plethora of widely differing design styles. The core of Ptolemy is a set of object-oriented class definitions that makes a few assumptions about the system to be modeled; rather, standard interfaces are provided for generic objects and more specialized, application-specific objects are derived from these. A basic abstraction in Ptolemy is the Domain, which realizes a computational model appropriate for a particular type of subsystem. Current examples of domains include synchronous and dynamic dataflow, discrete-event, and others appropriate for control software and embedded microcontrollers. Domains can be mixed as appropriate to realize and overall system simulation. Some current applications of Ptolemy include networking and transport, call-processing and signaling software, embedded microcontrollers, signal processing (including implementation in real-time), scheduling of parallel digital signal processors, board-level hardware timing simulation, and combinations of these.
980 citations
Book•
31 Dec 1992
TL;DR: This book presents a synthesis of recent works concerning reactive system design, based on Robin Milner's pioneering works about synchronous process algebras, which consists in considering that a program instantaneously reacts to events, or that the machine execution time is negligible with respect to the response delays of its environment.
Abstract: This book presents a synthesis of recent works concerning reactive system design. The term `reactive system' has been introduced in order to avoid ambiguities often involved with the term `real-time system' which, while being best-known and suggestive, has been assigned so many different meanings that it is almost inevitably misunderstood. Industrial Process control system, transportation control and supervision systems, signal processing systems, etc. are examples of the systems we have in mind. Four programming languages are presented, which share the same underlying synchronous model: based on Robin Milner's pioneering works about synchronous process algebras, this model consists in considering that a program instantaneously reacts to events, or that the machine execution time is negligible with respect to the response delays of its environment. Using this abstract point of view, the time behavior of a system can be formalized in a very simple and elegant way. The languages presented are ESTEREL, a textual imperative language; ARGOS, a graphical language inspired by STATECHARTS; and LUSTRE and SIGNAL, two declarative languages. After a tutorial description of the languages, illustrated by various examples, a set of related tools is presented: compilers to sequential and distributed code, silicon compilers, verification tools.
945 citations