Self-adaptive systems aim to satisfy system constraints in an environment with sudden parameter changes. Moreover, they enable new possibilities to cope with dynamic run-time requests. their self-adapting capabilities...
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ISBN:
(纸本)9781479988938
Self-adaptive systems aim to satisfy system constraints in an environment with sudden parameter changes. Moreover, they enable new possibilities to cope with dynamic run-time requests. their self-adapting capabilities lead to a highly dynamic system behavior which leads to development and run-time overheads. Additional real-time constraints increase the design space complexity further. the challenge is to reduce the complexity of application and system design. Recently, self-adaptive systems have been discovered for applications in emerging domains, such as the Internet of things or Cyber-Physical systems. Here, real-time support is often required for the respective systems. this paper surveys approaches to handle task scheduling/mapping, as well as resource management in these systems.
embedded system applications are becoming more complex, requiring increased memory. However additional physical memory increases system cost and power consumption. Virtual memory techniques such as paging, can make us...
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ISBN:
(纸本)9780769529752
embedded system applications are becoming more complex, requiring increased memory. However additional physical memory increases system cost and power consumption. Virtual memory techniques such as paging, can make use of low-power auxiliary memory, allowing applications increased memory for execution. Currently paging yields poor performance due to page swapping overheads. this paper presents a combined approach of using application hints along with an efficient page lock/release mechanism in the OS to reduce paging overheads. this makes paging a viable solution to support out-of-core embeddedreal-timeapplications. the Co-operative Application Specific Paging (CASP) mechanism presented works in conjunction with most existing page replacement policies, providing explicit support for applications via insertion of paging hints in the application source code. Both automatic and manual methods of inserting hints are described and evaluated. the benchmark results of a CASP implementation in the Linux 2.6.16 kernel have shown significant reduction in the number of page faults (22.3%) and a considerable improvement in application execution times (12,5%).
As real-timesystems become more prevalent, there is a need to guarantee that these increasingly complex systems perform as designed. One technique involves a static analysis to place an upper bound on worst-case exec...
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ISBN:
(纸本)9780769529752
As real-timesystems become more prevalent, there is a need to guarantee that these increasingly complex systems perform as designed. One technique involves a static analysis to place an upper bound on worst-case execution time (WCET). Tools for conducting this analysis typically require the developer to digest assembly opcodes, hexadecimal addresses, and other low-level details in order to make sense of the results. Java-specific processors offer a way out of this complexity. Such processors make Java software more predictable, and as a consequence, timing analysis of a real-time system becomes less computationally intensive. WCET analysis tools based on these processors can thus offer more powerful features at higher levels of abstraction. As proof of this concept, we present a tool for static WCET analysis of Java processors. Our performance measurements show that this tool makes WCET analysis interactive, offering continuous feedback to the developer in the form of back-annotations.
In this ongoing research, we investigate the mathematical properties of the scheduling theory and the real-time calculus and their relationship to each other.
ISBN:
(纸本)9781665441889
In this ongoing research, we investigate the mathematical properties of the scheduling theory and the real-time calculus and their relationship to each other.
In reality, peripheral devices often make a significant contribution to the power consumption of the entire system. An effective energy-efficient scheduling algorithm should consider not only the energy consumption of...
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ISBN:
(纸本)9780769529752
In reality, peripheral devices often make a significant contribution to the power consumption of the entire system. An effective energy-efficient scheduling algorithm should consider not only the energy consumption of the processor but also the usages of devices. In. this paper we explore energy-efficient scheduling of periodic real-time tasks in a system with a dynamic-voltage-scaling (DVS) processor and multiple non-DVS system devices. We consider systemsthat any device used by a task remains operating while the task is active. We propose scheduling algorithms in the management of task preemption to reduce the energy consumption of devices. Simulation results show that our proposed algorithms could not only reduce the number of task preemption significantly but also minimize the energy consumption, compared to earliest-deadline-first scheduling.
Remote health monitoring affords the possibility of improving the quality of health care by enabling relatively inexpensive out-patient care. However, remote health monitoring raises new a problem: the potential for d...
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ISBN:
(纸本)9780769529752
Remote health monitoring affords the possibility of improving the quality of health care by enabling relatively inexpensive out-patient care. However, remote health monitoring raises new a problem: the potential for data explosion in health care systems. To address this problem, the remote health monitoring systems must be integrated with analysis tools that provide automated trend analysis and event detection in realtime. In this paper, we propose an overview of Century, an extensible framework for analysis of large numbers of remote sensor-based medical data streams.
In this paper, we propose a novel fault-tolerant technique, which is seamlessly integrated with fixed priority-based scheduling algorithm to explore redundancies to enhance schedulability in fault-tolerant and real-ti...
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ISBN:
(纸本)9780769529752
In this paper, we propose a novel fault-tolerant technique, which is seamlessly integrated with fixed priority-based scheduling algorithm to explore redundancies to enhance schedulability in fault-tolerant and real-time distributed systems. Our fault-tolerant technique makes use of the primaiy-backup scheme to tolerate permanent hardware failures. Most importantly, the proposed technique (referred to as Tercos) terminates the execution of active backup copies when corresponding primary copies are successfully completed, therefore Tercos can reduce scheduling lengths in fault-free scenario to enhance schedulability by virtue of executing portions of active backup copies in passive forms. Experimental results show that compared with existing algorithm in literature, Tercos can significantly improve schedulability by up to 17.0% (with an average of 9.7 %).
Model Driven Engineering provides facilities to tackle complexity in real-timesystems, from early requirements capture to validation & verification down to code generation. We note that models are built from a sy...
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ISBN:
(纸本)9780769537870
Model Driven Engineering provides facilities to tackle complexity in real-timesystems, from early requirements capture to validation & verification down to code generation. We note that models are built from a system perspective, and resources are allocated to meet communication, energy or scheduling constraints. Yet, it is seldom optimal. In this paper, we explore transformations applied at model-level that preserve schedulability of the system, yet reduce the overall resource consumption. We use A AD L as input formalism. By automating this process, we show how to transition from a system view to an implementation view, closer to actual hardware constraints.
Given the major advantages of productivity and safety, the use of garbage collection (GC) in real-timesystems has gained increasing attention. Guaranteeing garbage collection activities' worst-case execution time...
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ISBN:
(纸本)9780769529752
Given the major advantages of productivity and safety, the use of garbage collection (GC) in real-timesystems has gained increasing attention. Guaranteeing garbage collection activities' worst-case execution time (WCET) is necessary for a real-time system to perform scheduling and schedulability analysis. this paper describes a detailed GC cost model for incremental mark-and-sweep GC exemplified by a modified Boehm-Demers-Weiser (BDW) collector the GC cost model computes the WCET for garbage collection in terms of (1) the performance of collector operations and (2) the garbage collection load offered by a real-time task. Separating these aspects is a step along the road to an engineering approach to garbage collection in real-timesystems, allowing prediction of system, behavior from knowledge of component behavior and environmental specifications. the model incorporates the cost of write barriers that are needed to support incremental GC. To be useful for real-timesystems, a model's predicted WCET must be no less than the actual WCET However unreasonably large overestimates are also problematic as they may lead to the incorrect conclusion that the application cannot be feasibly scheduled. A pessimism metric assesses the degree to which the model's predictions exceed the measured worst-case cost in particular instances.
Traditionally, implementations of dependable real-timesystems have targeted CPUs, with application level concurrency implemented as pseudo-concurrency on the CPU. For such systems, much research has addressed timing ...
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ISBN:
(纸本)9780769529752
Traditionally, implementations of dependable real-timesystems have targeted CPUs, with application level concurrency implemented as pseudo-concurrency on the CPU. For such systems, much research has addressed timing and resource analysis to enable offline guarantees regarding actual worst-case run-time performance. three major weaknesses exist withthe traditional implementation method. Firstly, analysis is post-hoc, after application compilation and worst-case execution time analysis. Secondly, timing analysis is pessimistic and difficult, due to the unpredictable nature of complex CPUs. thirdly, the compilation process is largely non-traceable, in that it is difficult to relate object code back to source code (which introduces verification difficulties in safety-critical systems). this paper addresses these three problems with an implementation approach and analysis method that: enables timing and space properties to be established directly from source (not after compilation);provides a deterministic and traceable implementation to ease verification;and enables non-pessimistic timing analysis of the implementation as no CPU is utilised. As an exemplar of the approach, the compilation of a standard real-time safely-critical subset of Ada. to a circuit (implemented on Field Programmable Gate Array) is presented.
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