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Exact Schedulability Test for global-EDF Scheduling of Periodic Hard Real-Time Tasks on Identical Multiprocessors  [PDF]
Jo?l Goossens,Patrick Meumeu Yomsi
Computer Science , 2010,
Abstract: In this paper we consider the scheduling problem of hard real-time systems composed of periodic constrained-deadline tasks upon identical multiprocessor platforms. We assume that tasks are scheduled by using the global-EDF scheduler. We establish an exact schedulability test for this scheduler by exploiting on the one hand its predictability property and by providing on the other hand a feasibility interval so that if it is possible to find a valid schedule for all the jobs contained in this interval, then the whole system will be stamped feasible. In addition, we show by means of a counterexample that the feasibility interval, and thus the schedulability test, proposed by Leung [Leung 1989] is incorrect and we show which arguments are actually incorrect.
Schedulability Test for Soft Real-Time Systems under Multiprocessor Environment by using an Earliest Deadline First Scheduling Algorithm  [PDF]
Jagbeer Singh,Satyendra Prasad Singh
Computer Science , 2012,
Abstract: This paper deals with the study of Earliest Deadline First (EDF) which is an optimal scheduling algorithm for uniprocessor real time systems use for scheduling the periodic task in soft real-time multiprocessor systems. In hard real-time systems, a significant disparity exists EDF-based schemes and RMA scheduling (which is the only known way of optimally scheduling recurrent real-time tasks on multiprocessors): on M processors, all known EDF variants have utilization-based schedulability bounds of approximately M/2, while RMA algorithms can fully utilize all processors. This is unfortunate because EDF based algorithms entail lower scheduling and task migration overheads. In work on hard real-time systems, it has been shown that this disparity in Schedulability can be lessened by placing caps on per task utilizations. Our main contribution is a new EDF based scheme that ensures bounded deadline tardiness. In this scheme, per-task utilizations must be focused,but overall utilization need not be stricted. Our scheme should enable a wide range of soft real-time applications to be scheduled with no constraints on total utilization. Also propose techniques and heuristics that can be used to reduce tardiness as well as increase the efficiency of task.
Efficient Feasibility Analysis for Real-Time Systems with EDF Scheduling  [PDF]
Karsten Albers,Frank Slomka
Computer Science , 2007,
Abstract: This paper presents new fast exact feasibility tests for uniprocessor real-time systems using preemptive EDF scheduling. Task sets which are accepted by previously described sufficient tests will be evaluated in nearly the same time as with the old tests by the new algorithms. Many task sets are not accepted by the earlier tests despite them beeing feasible. These task sets will be evaluated by the new algorithms a lot faster than with known exact feasibility tests. Therefore it is possible to use them for many applications for which only sufficient test are suitable. Additionally this paper shows that the best previous known sufficient test, the best known feasibility bound and the best known approximation algorithm can be derived from these new tests. In result this leads to an integrated schedulability theory for EDF.
A Fault-Tolerant Scheduling Algorithm Based on EDF for Distributed Control Systems

LIU Huai,FEI Shu-Min,

软件学报 , 2003,
Abstract: In recent result, the fault-tolerant scheduling algorithm almost requires that all task's periods are the same and equal to their deadlines, but in fact the periods are not the same in many cases. According to the characteristics of distributed control systems and the technique of primary/backup copies, based on EDF algorithm the novel fault-tolerant scheduling algorithm is proposed in this paper. The algorithm can deal with the different periods of all tasks. By using setting their deadlines the problem that execution times of primary and backup copies are not overlap can be controlled. The method for setting deadlines of primary and backup copies is given and the schedulability of task set is analyzed. The maximal utilization of task set and the minimal number of processor are investigated. The result of simulation shows that the algorithm is effective.
Experimental Software Schedulability Estimation For Varied Processor Frequencies  [PDF]
Sampsa Fabritius,Raimondas Lencevicius,Edu Metz,Alexander Ran
Computer Science , 2003,
Abstract: This paper describes a new approach to experimentally estimate the application schedulability for various processor frequencies. We use additional workload generated by an artificial high priority routine to simulate the frequency decrease of a processor. Then we estimate the schedulability of applications at different frequencies. The results of such estimation can be used to determine the frequencies and control algorithms of dynamic voltage scaling/dynamic frequency scaling (DVS/DFS) implementations. The paper presents a general problem description, the proposed schedulability estimation method, its analysis and evaluation.
Parallel Execution of Prolog on Shared-Memory Multiprocessors
Gao Yaoqing Wang Dingxing Zheng Weimin Shen Meiming Deptof Computer Science,Technology,Tsinghua University,Beijing Huang Zhiyi Hu Shouren Deptof Computer Science,Changsha Institute of Technology,Changsha,Hunan Giotto Levi Dipartimento di Informatica,Universita di PisaCorso Italia,- Pisa,Italy,
Gao Yaoqing
,Wang Dingxing,Zheng Weimin,Shen Meiming,Huang Zhiyi,Hu Shouren,Giotto Levi

计算机科学技术学报 , 1993,
Abstract: Logic programs offer many opportunities for the exploitation of parallelism.But the parallel execution of a task incurs various overheads This paper focuses on the issues relevant to parallelizing Prolog on shared-memory multiprocessors efficiently.
Integrating Schedulability Analysis with UML-RT  [PDF]
Qimin Gao,Lyndon J Brown,Luiz Fernando Capretz
Computer Science , 2015,
Abstract: The use of object oriented techniques and methodologies for the design of real-time control systems appear to be necessary in order to deal with the increasing complexity of such systems. Recently many object-oriented methods have been used for the modeling and design of real-time control systems. We believe that an approach that integrates the advancements in both object modeling and design methods, and real-time scheduling theory is the key to successful use of object oriented technology for real-time software. However, past approaches to integrate the two either restrict the object models, or do not allow sophisticated schedulability analysis techniques. In this paper we show how schedulability analysis can be integrated with object-oriented design; we develop the schedulability and feasibility analysis method for the external messages that may suffer release jitter due to being dispatched by a tick driven scheduler in real-time control system, and we also develop the scheduliability method for sporadic activities, where message arrive sporadically then execute periodically for some bounded time. This method can be used to cope with timing constraints in complex real-time control systems.
CCNoC:Cache-Coherent Network on Chip for Chip Multiprocessors
CCNoC: Cache-Coherent Network on Chip for Chip Multiprocessors

Jing-Lei Wang,Yi-Bo Xue,Hai-Xia Wang,Chong-Min Li,Dong-Sheng Wang,

计算机科学技术学报 , 2010,
Abstract: As the number of cores in chip multiprocessors(CMPs) increases,cache coherence protocol has become a key issue in integration of chip multiprocessors.Supporting cache coherence protocol in large chip multiprocessors still faces three hurdles:design complexity,performance and scalability.This paper proposes Cache Coherent Network on Chip(CCNoC),a scheme that decouples cache coherency maintenance from processors and shared L2 caches and implements it completely in network on chip to free up processors and sha...
Heavy traffic analysis for EDF queues with reneging  [PDF]
?ukasz Kruk,John Lehoczky,Kavita Ramanan,Steven Shreve
Mathematics , 2011, DOI: 10.1214/10-AAP681
Abstract: This paper presents a heavy-traffic analysis of the behavior of a single-server queue under an Earliest-Deadline-First (EDF) scheduling policy in which customers have deadlines and are served only until their deadlines elapse. The performance of the system is measured by the fraction of reneged work (the residual work lost due to elapsed deadlines) which is shown to be minimized by the EDF policy. The evolution of the lead time distribution of customers in queue is described by a measure-valued process. The heavy traffic limit of this (properly scaled) process is shown to be a deterministic function of the limit of the scaled workload process which, in turn, is identified to be a doubly reflected Brownian motion. This paper complements previous work by Doytchinov, Lehoczky and Shreve on the EDF discipline in which customers are served to completion even after their deadlines elapse. The fraction of reneged work in a heavily loaded system and the fraction of late work in the corresponding system without reneging are compared using explicit formulas based on the heavy traffic approximations. The formulas are validated by simulation results.
A Heuristic EDF Uplink Scheduler for Real Time Application in WiMAX Communication  [PDF]
Nidhi Lal,Anurag Prakash Singh,Shishupal Kumar,Shikha Mittal,Meenakshi Singh
Computer Science , 2015,
Abstract: WiMAX, Worldwide Interoperability for Microwave Access, is a developing wireless communication scheme that can provide broadband access to large-scale coverage. WiMAX belongs to the family of standards of IEEE-802.16. To satisfy user demands and support a new set of real time services and applications, a realistic and dynamic resource allocation algorithm is mandatory. One of the most efficient algorithm is EDF (earliest deadline first). But the problem is that when the difference between deadlines is large enough, then lower priority queues have to starve. So in this paper, we present a heuristic earliest deadline first (H-EDF) approach of the uplink scheduler of the WiMAX real time system. This H-EDF presents a way for efficient allocation of the bandwidth for uplink, so that bandwidth utilization is proper and appropriate fairness is provided to the system. We use Opnet simulator for implementing the WiMAX network, which uses this H-EDF scheduling algorithm. We will analysis the performance of the H-EDF algorithm in consideration with throughput as well as involvement of delay.
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