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Proceedings. 16th Euromicro Conference on Real-Time Systems, 2004. ECRTS 2004.

30 June-2 July 2004

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Displaying Results 1 - 25 of 37
  • Worst-case execution time analysis for dynamic branch predictors

    Publication Year: 2004, Page(s):215 - 222
    Cited by:  Papers (13)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (292 KB) | HTML iconHTML

    Branch prediction mechanisms are becoming commonplace within modern microprocessors. For developers of real-time control systems, the mechanisms present predictability problems. The reasons are they increase the difficulty in analysing software for its worst-case execution time without introducing unmanageable pessimism and they increase the variability of the software's execution times. In this p... View full abstract»

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  • QoS control strategies for high-quality video processing

    Publication Year: 2004, Page(s):3 - 12
    Cited by:  Papers (14)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (400 KB) | HTML iconHTML

    Video processing in software is often characterized by highly fluctuating, content-dependent processing times, and a limited tolerance for deadline misses. We present an approach that allows close-to-average-case resource allocation to a single video processing task, based on asynchronous, scalable processing, and QoS adaptation. The QoS adaptation balances different QoS parameters that can be tun... View full abstract»

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  • A new sufficient feasibility test for asynchronous real-time periodic task sets

    Publication Year: 2004, Page(s):204 - 211
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (349 KB) | HTML iconHTML

    The problem of feasibility analysis for asynchronous periodic task sets (i.e. where tasks can have an initial offset) is known to be co-NP-complete in the strong sense. A sufficient pseudo-polynomial test has been proposed by Baruah et al., which consists in analyzing the feasibility of the corresponding synchronous task set (i.e. all offsets are set equal to 0) for which a pseudo-polynomial test ... View full abstract»

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  • A variable rate execution model

    Publication Year: 2004, Page(s):135 - 143
    Cited by:  Papers (14)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (457 KB) | HTML iconHTML

    We present a task model for adaptive real-time tasks in which a task's execution rate requirements are allowed to change at any time. The model, variable rate execution (VRE), is an extension of the rate-based execution (RBE) model. We relax the constant execution rate assumption of canonical real-time task models by allowing both the worst case execution time (WCET) and the period to be variable.... View full abstract»

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  • Biasing effects in schedulability measures

    Publication Year: 2004, Page(s):196 - 203
    Cited by:  Papers (55)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (441 KB) | HTML iconHTML

    The performance of a schedulabilty test is typically evaluated by generating a huge number of synthetic task sets and then computing the fraction of those that pass the test with respect to the total number of feasible ones. The resulting ratio, however, depends on the metrics used for evaluating the performance and on the method for generating random task parameters. In particular, an important f... View full abstract»

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  • Multiprocessor energy-efficient scheduling with task migration considerations

    Publication Year: 2004, Page(s):101 - 108
    Cited by:  Papers (26)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (407 KB) | HTML iconHTML

    This paper targets energy-efficient scheduling of tasks over multiple processors, where tasks share a common deadline. Distinct from many research results on heuristics-based energy-efficient scheduling, we propose approximation algorithms with different approximation bounds for processors with/without constraints on the maximum processor speed, where no task migration is allowed. When there is no... View full abstract»

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  • Generalized pre-scheduler

    Publication Year: 2004, Page(s):127 - 134
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (383 KB)

    A preschedule is a list of "executives" generated offline for a set of time-driven jobs. If in addition there exists event-driven workload competing for resources, sufficient slacks must be embedded in a valid preschedule. A prescheduler was defined in Wang et al. (2003) with the following assumptions: the competing workload is modeled as sporadic tasks and the time-driven jobs to be prescheduled ... View full abstract»

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  • An event stream driven approximation for the analysis of real-time systems

    Publication Year: 2004, Page(s):187 - 195
    Cited by:  Papers (50)  |  Patents (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (295 KB) | HTML iconHTML

    This paper presents a new approach to understand the event stream model. Additionally a new approximation algorithm for the feasibility test of the sporadic and the generalized multiframe task system scheduled by earliest deadline first is presented. The new algorithm has polynomial complexity to solve the problem of schedulability analysis. The approximation error of the algorithm is bounded. In ... View full abstract»

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  • Optimized slowdown in real-time task systems

    Publication Year: 2004, Page(s):155 - 164
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (383 KB) | HTML iconHTML

    Slowdown factors determine the extent of slowdown a computing system can experience based on functional and performance requirements. Dynamic voltage scaling (DVS) of a processor based on slowdown factors can lead to considerable energy savings. We address the problem of computing slowdown factors for dynamically scheduled tasks with specified deadlines. We present an algorithm to compute a near o... View full abstract»

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  • Schedulability-driven partitioning and mapping for multi-cluster real-time systems

    Publication Year: 2004, Page(s):91 - 100
    Cited by:  Papers (8)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (418 KB)

    We present an approach to partitioning and mapping for multicluster embedded systems consisting of time-triggered and event-triggered clusters, interconnected via gateways. We have proposed a schedulability analysis for such systems, including a worst-case queuing delay analysis for the gateways responsible for routing intercluster traffic. Based on this analysis, we address design problems charac... View full abstract»

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  • Integrating model-based design and preemptive scheduling in mixed time- and event-triggered systems

    Publication Year: 2004, Page(s):119 - 126
    Cited by:  Papers (22)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (258 KB) | HTML iconHTML

    Model-based design is advocated as the method of choice when dealing with critical systems as well as high quality systems. However, it often abstracts implementation details such as execution times. This can be a problem when dealing with urgent events whose implementation requires preemptive scheduling. In this paper, we propose an intertask communication mechanism on top of a fixed-priority dea... View full abstract»

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  • Energy-efficient policies for request-driven soft real-time systems

    Publication Year: 2004, Page(s):175 - 183
    Cited by:  Papers (10)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (324 KB) | HTML iconHTML

    Computing systems, ranging from small battery-operated embedded systems to more complex general purpose systems, are designed to satisfy various computation demands in some acceptable time. In doing so, the system is responsible for scheduling jobs/requests in a dynamic fashion. In addition, with power consumption recently becoming a critical issue, most systems are also responsible for their own ... View full abstract»

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  • Managing quality-of-control performance under overload conditions

    Publication Year: 2004, Page(s):53 - 60
    Cited by:  Papers (15)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (359 KB) | HTML iconHTML

    A common method for dealing with overload conditions in periodic task systems is to reduce the load by enlarging activation periods. When a periodic task implements a digital controller, however, the variation applied on the task period also affects the control law, which needs to be recomputed for the new activation rate. If computing a new control law requires too much time to be performed at ru... View full abstract»

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  • Analysis of tree-shaped transactions in distributed real time systems

    Publication Year: 2004, Page(s):239 - 248
    Cited by:  Papers (10)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (344 KB) | HTML iconHTML

    A worst case response time analysis exploiting precedence constraints between fixed priority scheduled tasks in tree-shaped transactions is presented. The algorithm extends existing methods for analysis of linear transactions allowing a wider range of systems, in which tasks may trigger more than one succeeding task on their completion, i.e. the transactions form trees. It also improves existing m... View full abstract»

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  • Stabilizing execution time of user processes by bottom half scheduling in Linux

    Publication Year: 2004, Page(s):71 - 78
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (568 KB) | HTML iconHTML

    The CPU time allocated to user processes is rendered inaccurate by an unexpectedly and frequently occurring interrupt and a bottom half that consumes most interrupt processing time. Additionally, when the time consumed in the kernel mode greatly fluctuates with interrupt processing, the scheduler cannot distribute CPU time to user processes normally. This problem can dramatically distort the stabl... View full abstract»

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  • Collaborative resource allocation in wireless sensor networks

    Publication Year: 2004, Page(s):35 - 44
    Cited by:  Papers (22)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (932 KB) | HTML iconHTML

    Traditional real-time resource allocation algorithms assume that the available resources in a system such as total CPU and network bandwidth do not change over time. However, in wireless sensor networks, the amount of available resources on the devices and the communication channel may not be constant for all times: for instance, a node can be turned off in some time intervals to increase its batt... View full abstract»

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  • Static determination of probabilistic execution times

    Publication Year: 2004, Page(s):223 - 230
    Cited by:  Papers (23)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (364 KB) | HTML iconHTML

    Most previous research done in probabilistic schedulability analysis assumes a known distribution of execution times for each task of a real-time application. This is however not trivial to determine it with a high level of confidence. Methods based on measurements are often biased since not in general exhaustive on all the possible execution paths, whereas methods based on static analysis are mos... View full abstract»

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  • Reducing the number of preemptions in fixed priority scheduling

    Publication Year: 2004, Page(s):144 - 152
    Cited by:  Papers (12)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (317 KB) | HTML iconHTML

    Fixed priority scheduling (FPS) has been widely studied and used in a number of applications, mostly due to its flexibility, simple run-time mechanism and small overhead. However, preemption related overhead in FPS may cause undesired high processor utilization, high energy consumption, or, in some cases, even infeasibility. In this paper, we propose a method to reduce the number of preemptions in... View full abstract»

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  • TLSF: a new dynamic memory allocator for real-time systems

    Publication Year: 2004, Page(s):79 - 88
    Cited by:  Papers (32)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (313 KB)

    Dynamic storage allocation (DSA) algorithms play an important role in the modern software engineering paradigms and techniques (such as object oriented programming). Using DSA increases the flexibility and functionalities of applications. There exists a large number of references to this particular issue in the literature. However, the use of DSA has been considered a source of indeterminism in th... View full abstract»

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  • Executing aperiodic jobs in a multiprocessor constant-bandwidth server implementation

    Publication Year: 2004, Page(s):109 - 116
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (799 KB) | HTML iconHTML

    The constant bandwidth server (CBS) framework can be implemented on a preemptive uniprocessor platform to make full use of the computing capacity of the platform; when implemented upon a preemptive multiprocessor platform, however, it is known that the schedulable utilization is strictly less than the capacity of the platform. The issue of using the excess processing capacity is addressed here, an... View full abstract»

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  • Improved prediction for Web server delay control

    Publication Year: 2004, Page(s):61 - 68
    Cited by:  Papers (24)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (405 KB) | HTML iconHTML

    Control methods are being used increasingly for uncertainty management and QoS in modern Web server systems. Previous approaches have suggested combined feedforward and feedback control strategies, using queuing theory for feedforward delay prediction. While queuing theory allows one to predict delay as a function of arrival and service rates, the prediction applies only to long-term averages, and... View full abstract»

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  • On energy-constrained real-time scheduling

    Publication Year: 2004, Page(s):165 - 174
    Cited by:  Papers (12)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (316 KB) | HTML iconHTML

    In this paper, we explore the feasibility and performance optimization problems for real-time systems that must remain functional during an operation/mission with a fixed, initial energy budget. We show that the feasibility problem is NP-hard in the context of systems with dynamic voltage scaling (DVS) capability and discrete speed levels. Then, we focus on energy-constrained periodic task systems... View full abstract»

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  • Maintaining data freshness in distributed real-time databases

    Publication Year: 2004, Page(s):251 - 260
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (358 KB) | HTML iconHTML

    Many real-time systems need to maintain fresh views which are derived from shared data that are distributed among multiple sites. When a base data item changes, all derived views that are based on it need to be recomputed. There are two major derived data re-computation strategies - immediate update and on-demand update. However, they both have their advantages and limitations. In this paper, we s... View full abstract»

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  • Quality aware MPEG-2 stream adaptation in resource constrained systems

    Publication Year: 2004, Page(s):23 - 32
    Cited by:  Papers (16)  |  Patents (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (337 KB) | HTML iconHTML

    A number of algorithms have been presented for handling software decoding of MPEG-2 streams based on buffering or rate adjustment focusing on providing good average quality. The potentially arising drops in quality are tolerated, e.g., in transmissions over the Internet; they cannot be accepted in high quality consumer products: these mandate real-time methods. When resources, such as processing p... View full abstract»

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  • Comparing real-time communication under electromagnetic interference

    Publication Year: 2004, Page(s):45 - 52
    Cited by:  Papers (19)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (281 KB) | HTML iconHTML

    The contribution of this paper is threefold. First, an improvement to a previously published paper on the timing analysis of controller area network (CAN) in the presence of transient network faults is presented. A probabilistic fault model is considered, where random faults from electromagnetic interference occur according to a Poisson distribution. The analysis provides worst case response times... View full abstract»

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