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Analysis and Synthesis of CommunicationIntensive Heterogeneous RealTime Systems
 LINKÖPING STUDIES IN SCIENCE AND TECHNOLOGY, PH.D. DISSERTATION NO. 833
, 2003
"... EMBEDDED COMPUTER SYSTEMS are now everywhere: from alarm clocks to PDAs, from mobile phones to cars, almost all the devices we use are controlled by embedded computer systems. An important class of embedded computer systems is that of realtime systems, which have to fulfill strict timing requiremen ..."
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Cited by 33 (11 self)
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EMBEDDED COMPUTER SYSTEMS are now everywhere: from alarm clocks to PDAs, from mobile phones to cars, almost all the devices we use are controlled by embedded computer systems. An important class of embedded computer systems is that of realtime systems, which have to fulfill strict timing requirements. As realtime systems become more complex, they are often implemented using distributed heterogeneous architectures. The main objective of this thesis is to develop analysis and synthesis methods for communicationintensive heterogeneous hard realtime systems. The systems are heterogeneous not only in terms of platforms and communication protocols, but also in terms of scheduling policies. Regarding this last aspect, in this thesis we consider timedriven systems, eventdriven systems, and a combination of both, called multicluster systems. The analysis takes into
Regular Specifications of Resource Requirements for Embedded Control Software
, 2008
"... For embedded control systems, a schedule for the allocation of resources to a software component can be described by an infinite word whose ith symbol models the resources used at the ith sampling interval. Dependency of performance on schedules can be formally modeled by an automaton (ωregular lan ..."
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Cited by 26 (7 self)
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For embedded control systems, a schedule for the allocation of resources to a software component can be described by an infinite word whose ith symbol models the resources used at the ith sampling interval. Dependency of performance on schedules can be formally modeled by an automaton (ωregular language) which captures all the schedules that keep the system within performance requirements. We show how such an automaton is constructed for linear control designs and exponential stability or settling time performance requirements. Then, we explore the use of the automaton for online scheduling and for schedulability analysis. As a case study, we examine how this approach can be applied for the LQG control design. We demonstrate, by examples, that online schedulers can be used to guarantee performance in worstcase condition together with good performance in normal conditions. We also provide examples of schedulability analysis.
On the Complexity of Scheduling Conditional RealTime Code
 In Proc. 7th International Workshop on Algorithms and Data Structures (WADS), Lecture Notes in Computer Science 2125
, 2001
"... . Many realtime embedded systems involve a collection of independently ..."
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Cited by 25 (10 self)
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. Many realtime embedded systems involve a collection of independently
Schedulability Analysis for Systems with Data and Control Dependencies
 in Proceedings of the 12 th Euromicro Conference on RealTime Systems
, 2000
"... In this paper we present an approach to schedulability analysis for hard realtime systems with control and data dependencies. We consider distributed architectures consisting of multiple programmable processors, and the scheduling policy is based on a static priority preemptive strategy. Our model ..."
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Cited by 23 (3 self)
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In this paper we present an approach to schedulability analysis for hard realtime systems with control and data dependencies. We consider distributed architectures consisting of multiple programmable processors, and the scheduling policy is based on a static priority preemptive strategy. Our model of the system captures both data and control dependencies, and the schedulability approach is able to reduce the pessimism of the analysis by using the knowledge about control and data dependencies. Extensive experiments as well as a real life example demonstrate the efficiency of our approach. 1.
An Introduction to Control and Scheduling
 39TH IEEE CONFERENCE ON DECISION AND CONTROL
, 1999
"... The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling o ..."
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Cited by 20 (6 self)
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The report gives a stateoftheart survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling codesign, dynamic task adaptation, feedback scheduling, and scheduling of imprecise calculations. The report also presents the background, motivation, and research topics in the ARTES project “Integrated
The design of an edfscheduled resourcesharing open environment
 In RTSS
, 2007
"... We study the problem of executing a collection of independently designed and validated task systems upon a common platform comprised of a preemptive processor and additional shared resources. We present an abstract formulation of the problem and identify the major issues that must be addressed in or ..."
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Cited by 20 (1 self)
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We study the problem of executing a collection of independently designed and validated task systems upon a common platform comprised of a preemptive processor and additional shared resources. We present an abstract formulation of the problem and identify the major issues that must be addressed in order to solve this problem. We present (and prove the correctness of) algorithms that address these issues, and thereby obtain a design for an open realtime environment.
Approximate Schedulability Analysis
 In Proceedings of the IEEE RealTime Systems Symposium. IEEE Computer Society
, 2002
"... The schedulability analysis problem for many realistic task models is intractable. Therefore known algorithms either have exponential complexity or at best can be solved in pseudopolynomial time, thereby restricting the application of the concerned models to a large extent. We introduce the notion ..."
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Cited by 17 (4 self)
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The schedulability analysis problem for many realistic task models is intractable. Therefore known algorithms either have exponential complexity or at best can be solved in pseudopolynomial time, thereby restricting the application of the concerned models to a large extent. We introduce the notion of "approximate schedulability analysis" and show that if a small amount of "error" (which is specified as an input to the algorithm) can be tolerated in the decisions made by the algorithm, then this problem can be solved in polynomial time. Our algorithms are analogous to fully polynomial time approximation schemes in the context of optimization problems. We show that this concept of approximate schedulability analysis is fairly general and can be applied to any task model which satisfies certain "taskindependence " assumptions. Lastly, we substantiate our theoretical results with experimental evidence and clearly show the tradeoffs between the running time of the schedulability analysis and the error incurred for various values of the input error parameter.
Combinatorial Abstraction Refinement for Feasibility Analysis
 in Proc. of RTSS, 2013
"... Abstract Combinatorial explosion is a challenge for many analysis problems in the theory of hard realtime systems. One of these problems is static priority schedulability of workload models which are more expressive than the traditional periodic task model. Different classes of directed graphs hav ..."
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Cited by 10 (7 self)
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Abstract Combinatorial explosion is a challenge for many analysis problems in the theory of hard realtime systems. One of these problems is static priority schedulability of workload models which are more expressive than the traditional periodic task model. Different classes of directed graphs have been proposed in recent years to model structures like frames, branching and loops. In contrast to dynamic priority schedulers with pseudopolynomial time analysis methods, static priority schedulability has been shown to be intractable since it is strongly coNPhard already for the relatively simple class of cyclic digraphs. The core of this problem is the necessity to combine different behaviors of the participating tasks. We introduce a novel iterative approach to efficiently cope with this combinatorial explosion, called combinatorial abstraction refinement. In combination with other techniques it significantly reduces exponential growth of runtime for most inputs. We apply the method to static task priorities and demonstrate that a prototype implementation outperforms the stateofthe art pseudopolynomial analysis for dynamic priority feasibility. It further shows better scaling behavior for randomly generated problem instances. We extend the approach to nonpreemptive schedulers as well as static jobtype priorities where jobs of different types in the same task may be assigned different static priorities. Finally, we provide a general, abstract formulation of the algorithm, since we believe that this method can be applicable to a variety of combinatorial problems in the theory of realtime systems with certain abstraction structures.
On schedulability analysis of noncyclic generalized multiframe tasks
 In Proceedings of the 2010 22nd Euromicro Conference on RealTime Systems
, 2010
"... Abstract — The generalized multiframe (GMF) task has been proposed to model a task whose execution times, deadlines and minimum separation times are changed according to a specified pattern. In this paper we relax the assumption of having a specified activation pattern, this yields to noncyclic GMF ..."
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Cited by 9 (0 self)
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Abstract — The generalized multiframe (GMF) task has been proposed to model a task whose execution times, deadlines and minimum separation times are changed according to a specified pattern. In this paper we relax the assumption of having a specified activation pattern, this yields to noncyclic GMF task. In this context, current schedulability analysis techniques for GMF task sets under dynamic priority assignment cannot be used. This paper presents response time analysis of noncyclic GMF tasks executing on a uniprocessor according to earliest deadline first (EDF) scheduling policy. Also, a densitybased sufficient schedulability test for noncyclic GMF task sets is given. Finally an efficient approach is presented, for exact feasibility determination using computer simulation. Keywordscomponent: schedulability analysis, noncyclic GMF task, EDF. I.
Finding an upper bound on the increase in execution time due to contention on the memory bus in COTSbased multicore systems
 SIGBED Review
"... Abstract Contention on the memory bus in COTS based multicore systems isbecoming a major determining factor of the execution time of atask. Analyzing this extra execution time is nontrivial because(i) bus arbitration protocols in such systems are oftenundocumented and (ii) the times when the memor ..."
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Cited by 9 (2 self)
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Abstract Contention on the memory bus in COTS based multicore systems isbecoming a major determining factor of the execution time of atask. Analyzing this extra execution time is nontrivial because(i) bus arbitration protocols in such systems are oftenundocumented and (ii) the times when the memory bus isrequested to be used are not explicitly controlled by the operatingsystem scheduler; they are instead a result of cache misses.We present a method for finding an upper bound on the extraexecution time of a task due to contention on the memory bus in COTSbased multicore systems. This method makes no assumptions on the busarbitration protocol (other than assuming that it isworkconserving). AbstractContention on the memory bus in COTS based multicore systems is becoming a major determining factor of the execution time of a task. Analyzing this extra execution time is nontrivial because (i) bus arbitration protocols in such systems are often undocumented and (ii) the times when the memory bus is requested to be used are not explicitly controlled by the operating system scheduler; they are instead a result of cache misses. We present a method for finding an upper bound on the extra execution time of a task due to contention on the memory bus in COTS based multicore systems. This method makes no assumptions on the bus arbitration protocol (other than assuming that it is workconserving). Finding an Upper Bound on the Increase in Execution Time