We present a garbage collector scheduling algorithm for dynamic multiprocessor real-timesystems called GCMUA. the algorithm considers mutator activities that are subject to time/utility function time constraints, sto...
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ISBN:
(纸本)0769526764
We present a garbage collector scheduling algorithm for dynamic multiprocessor real-timesystems called GCMUA. the algorithm considers mutator activities that are subject to time/utility function time constraints, stochastic execution-time and memory demands, and overloads. We prove that GCMUA probabilistically lower bounds each mutator's accrued utility, lower bounds the total accrued utility, and upper bounds the assurances' sensitivity to variations in execution-time and memory demand estimates. Our simulation results confirm our analytical results.
Hierarchical scheduling frameworks have lately received a lot of attention for component-based design of complex real-timesystems. the specification of the resource reservation policy play a dominant role in such fra...
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ISBN:
(纸本)0769526764
Hierarchical scheduling frameworks have lately received a lot of attention for component-based design of complex real-timesystems. the specification of the resource reservation policy play a dominant role in such frameworks. In this context, the notion of real-time virtual resources results a very flexible representation of resource reservation schemes. We intend to combine the advantages offered by virtual resource scheduling with very general event models specified using real-time calculus. Our proposed framework permits resource partitioning to be extended to multiple levels and handles a wider range of scheduling algorithms and task models. In addition, it allows the handling of data dependencies between tasks from different task groups in the hierarchy.
Consider the problem of scheduling a set of periodically arriving tasks on a multiprocessor withthe goal of meeting deadlines. Processors are identical and have the same speed. Tasks can be preempted and they can mig...
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ISBN:
(纸本)0769526764
Consider the problem of scheduling a set of periodically arriving tasks on a multiprocessor withthe goal of meeting deadlines. Processors are identical and have the same speed. Tasks can be preempted and they can migrate between processors. We propose an algorithm with a utilization bound of 66% and with few preemptions. It can trade a higher utilization bound for more preemptions and in doing so it has a utilization bound of 100%.
. the real-time implementation of a controller typically introduces artefacts like delay and jitters that have not been considered at the design stage. As a consequence, the system behaves in a non-periodic manner, an...
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ISBN:
(纸本)0769526764
. the real-time implementation of a controller typically introduces artefacts like delay and jitters that have not been considered at the design stage. As a consequence, the system behaves in a non-periodic manner, and the real performance is degraded with respect to the expected response. this paper proposes a hybrid task model to reduce the impact of the scheduling on the control performance. For a large batch of typical plants, we analyze how sensitive the control system is to jitter when the sampling rate is slow or fast compared to the bandwidth of the system.
real-timeembeddedsystems are increasingly being networked. In distributed real-timeembeddedapplications, e.g., electric grid management and command and control applications, it is required to not only meet real-ti...
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ISBN:
(纸本)0769526764
real-timeembeddedsystems are increasingly being networked. In distributed real-timeembeddedapplications, e.g., electric grid management and command and control applications, it is required to not only meet real-time constraints but also support the data confidentiality, integrity, and authenticity. Unfortunately, in general, cryptographic functions are computationally expensive, possibly causing deadline misses in real-timeembeddedsystems with limited resources. As a basis for cost-effective security support in real-timeembeddedsystems, we define a quantitative notion of Strength of Defense (SoD). Based on the SoD concept, we propose a novel adaptive security policy in which the SoD can be degraded by decreasing the cryptographic key length for certain tasks, if necessary, to improve the success ratio under overload conditions. Our approach is lightweight. the time complexity of our approach is linear and its amortized version has the constant overhead per Sol) adaptation period. Moreover, our approach supports desirable security features requiring an attacker to do extra work to find the cryptographic key. In the performance evaluation, we show that our approach can considerably improve the success ratio due to controlled Sol) degradation under overload.
In some real-timeapplications, it is desirable to trade off precision for timeliness. For such systems, considered typically under the Imprecise Computation model, a function assigns reward to the application dependi...
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ISBN:
(纸本)0769526764
In some real-timeapplications, it is desirable to trade off precision for timeliness. For such systems, considered typically under the Imprecise Computation model, a function assigns reward to the application depending on the amount of computation allotted to it. Also, many such applications ran on battery-powered devices where the energy consumption is of utmost importance. We address in this paper the problem of energy minimization for Imprecise-Computation systemsthat have reward and time constraints. We propose a Quasi-Static (QS) approach that exploits, with low on-line overhead, the dynamic slack that arises from variations in the actual number of execution cycles: first, at design-time, a set of solutions are computed and stored (off-line phase);second, the selection among the precomputed assignments is left for ran-time, based on actual values of time and reward (on-line phase).
To build a "correct" implementation from a model of a concurrent real-time system, it is important to understand the relation between the properties of the model and of its corresponding implementation. In t...
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ISBN:
(纸本)0769526764
To build a "correct" implementation from a model of a concurrent real-time system, it is important to understand the relation between the properties of the model and of its corresponding implementation. In this paper, the behaviour of a system is described withtimed action sequences. Based on a notion of distance that expresses the observable property preservation between timed action sequences, we show that a stronger observable property preservation between model and implementation is obtained when urgency on the execution of observable actions is imposed over the execution of unobservable ones. Furthermore, we present a model synthesis approach and, by means of a case study, we show how it can be applied in the synthesis of real-timesystems.
In this paper we analyze the traditional model of interrupt management and its inability to incorporate the reliability and temporal predictability demanded by real-timesystems. As a result of this analysis, we propo...
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ISBN:
(纸本)0769526764
In this paper we analyze the traditional model of interrupt management and its inability to incorporate the reliability and temporal predictability demanded by real-timesystems. As a result of this analysis, we propose a model that and task integrates interrupts tasks handling. We introduce a novel implementation of this model that uses an adaptation of the optimistic interrupt protection technique [12] for achieving predictability and low overhead. the detailed design of a flexible and portable kernel interrupt subsystem for this integrated optimistic model is presented. We make a schedulability analysis to evaluate the optimistic integrated model and perform experiments to verify its deterministic behavior and its overhead.
the estimation of the Worst-Case Execution time of hard real-timeapplications becomes very hard as more and more complex processors are used in realtimesystems. In modern architectures, estimating the execution time...
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ISBN:
(纸本)0769526764
the estimation of the Worst-Case Execution time of hard real-timeapplications becomes very hard as more and more complex processors are used in realtimesystems. In modern architectures, estimating the execution time of a single basic block is not trivial due to possible timing anomalies linked to out-of-order execution. the influence of preceding basic blocks on the pipeline state also has to be accounted for. Recently, graphs have been used to model the execution of a block on a dynamically-scheduled pipelined processor [11]. In this paper we extend this model to express instruction-level parallelism so that superscalar processors with multiple functional units can be analyzed. Simulation results show how this extended model estimates WCETs tightly even when a realistic processor is considered. they also give an insight into the complexity of the model in terms of analysis time.
Hardware/software codesign involves various design problems including system specification, design space exploration, hardware/software co-verification, and system synthesis. A codesign environment is a software tool ...
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ISBN:
(纸本)0769526764
Hardware/software codesign involves various design problems including system specification, design space exploration, hardware/software co-verification, and system synthesis. A codesign environment is a software tool that facilitates capabilities to solve these design problems. this paper presents the PeaCE codesign environment mainly targeting for multimedia applications withreal-time constraints. PeaCE specifies the system behavior with a heterogeneous composition of three models of computation. the PeaCE environment provides seamless co-design flow from functional simulation to system synthesis, utilizing the features of the formal models maximally during the whole design process. Preliminary experiments withreal examples prove the viability of the proposed technique.
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