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Algorithms and Complexity Concerning the Preemptive Scheduling of Periodic, RealTime Tasks on One Processor
 RealTime Systems
, 1990
"... We investigate the preemptive scheduling of periodic, realtime task systems on one processor. First, we show that when all parameters to the system are integers, we may assume without loss of generality that all preemptions occur at integer time values. We then assume, for the remainder of the pape ..."
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Cited by 248 (15 self)
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We investigate the preemptive scheduling of periodic, realtime task systems on one processor. First, we show that when all parameters to the system are integers, we may assume without loss of generality that all preemptions occur at integer time values. We then assume, for the remainder of the paper, that all parameters are indeed integers. We then give as our main lemma both necessary and sufficient conditions for a task system to be feasible on one processor. Although these conditions cannot, in general, be tested efficiently (unless P = NP), they do allow us to give efficient algorithms for deciding feasibility on one processor for certain types of periodic task systems. For example, we give a pseudopolynomial time algorithm for synchronous systems whose densities are bounded by a fixed constant less than 1. This algorithm represents an exponential improvement over the previous best algorithm. We also give a polynomialtime algorithm for systems having a fixed number of distinct typ...
StaticPriority Scheduling on Multiprocessors
 In Proc. 22nd IEEE RealTime Systems Symposium
, 2001
"... The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical multiprocessors is considered. A scheduling algorithm is proposed for staticpriority scheduling of such systems; this algorithm is a simple extension of the uniprocessor ratemonotonic scheduling algo ..."
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Cited by 138 (17 self)
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The preemptive scheduling of systems of periodic tasks on a platform comprised of several identical multiprocessors is considered. A scheduling algorithm is proposed for staticpriority scheduling of such systems; this algorithm is a simple extension of the uniprocessor ratemonotonic scheduling algorithm. It is proven that this algorithm successfully schedules any periodic task system with a worstcase utilization no more than a third the capacity of the multiprocessor platform; for the special case of harmonic periodic task systems, the algorithm is proven to successfully schedule any system with a worstcase utilization of no more than half the platform capacity.
A survey of hard realtime scheduling for multiprocessor systems
 ACM COMPUTING SURVEYS
, 2011
"... This survey covers hard realtime scheduling algorithms and schedulability analysis techniques for homogeneous multiprocessor systems. It reviews the key results in this field from its origins in the late 1960s to the latest research published in late 2009. The survey outlines fundamental results ab ..."
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Cited by 99 (9 self)
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This survey covers hard realtime scheduling algorithms and schedulability analysis techniques for homogeneous multiprocessor systems. It reviews the key results in this field from its origins in the late 1960s to the latest research published in late 2009. The survey outlines fundamental results about multiprocessor realtime scheduling that hold independent of the scheduling algorithms employed. It provides a taxonomy of the different scheduling methods, and considers the various performance metrics that can be used for comparison purposes. A detailed review is provided covering partitioned, global, and hybrid scheduling algorithms, approaches to resource sharing, and the latest results from empirical investigations. The survey identifies open issues, key research challenges, and likely productive research directions.
Joint Scheduling of Distributed Complex Periodic and Hard Aperiodic Tasks in Statically Scheduled Systems
 IN PROC. 16TH REALTIME SYSTEMS SYMPOSIUM
, 1995
"... In this paper we present algorithms for the joint scheduling of periodic and aperiodic tasks in statically scheduled distributed realtime systems. Periodic tasks are precedence constrained, distributed, and communicating over the nodes of the systems. Both soft and hard aperiodic tasks are handled. ..."
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Cited by 73 (19 self)
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In this paper we present algorithms for the joint scheduling of periodic and aperiodic tasks in statically scheduled distributed realtime systems. Periodic tasks are precedence constrained, distributed, and communicating over the nodes of the systems. Both soft and hard aperiodic tasks are handled. After a static schedule has been created in a first step, the algorithms determine the amount and distribution of unused resources and leeway in it. These are then used to incorporate aperiodic tasks into the schedule by shifting the periodic tasks' execution, without violating their feasibility. Runtime mechanisms are simple and require only little memory. Processors and communication nodes can be utilized fully. The algorithm performs an optimal online guarantee algorithm for hard aperiodic tasks of O(N). An extensive simulation study exhibits very high guarantee ratios for various load and deadline scenarios, which underlines the efficiency of our method.
A Theory of RateBased Execution
 In Proceedings of the 20th IEEE RealTime Systems Symposium (RTSS
, 1999
"... * We present a task model for the realtime execution of eventdriven tasks in which no a priori characterization of the actual arrival rates of events is known; only the expected arrival rates of events is known. The model, called ratebased execution (RBE), is a generalization of Mok's spora ..."
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Cited by 69 (8 self)
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* We present a task model for the realtime execution of eventdriven tasks in which no a priori characterization of the actual arrival rates of events is known; only the expected arrival rates of events is known. The model, called ratebased execution (RBE), is a generalization of Mok's sporadic task model [14]. The RBE model is motivated naturally by distributed multimedia and digital signal processing applications. We derive necessary and sufficient conditions for determining the feasibility of an RBE task set and demonstrate that earliest deadline first (EDF) scheduling is an optimal scheduling algorithm for both preemptive and nonpreemptive execution environments, as well as hybrid environments wherein RBE tasks access shared resources. Our analysis of RBE tasks demonstrates a fundamental distinction between deadline based scheduling methods and static priority based methods. We show that for deadlinebased scheduling methods, feasibility is solely a function of the distribution o...
Resource reservation in dynamic realtime systems
 RealTime Systems
, 2004
"... Abstract. This paper focuses on the problem of providing ef®cient runtime support to multimedia applications in a realtime system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical realtime tasks (hard tasks) are guaranteed based on worstcase ex ..."
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Cited by 62 (13 self)
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Abstract. This paper focuses on the problem of providing ef®cient runtime support to multimedia applications in a realtime system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical realtime tasks (hard tasks) are guaranteed based on worstcase execution times and minimum interarrival times, multimedia tasks are served based on mean parameters.A novel bandwidth reservation mechanism (the constant bandwidth server) allows realtime tasks to execute in a dynamic environment under a temporal protection mechanism, so that each task will never exceed a prede®ned bandwidth, independently of its actual requests.The paper also discusses how the proposed server can be used for handling aperiodic tasks ef®ciently and how a statistical analysis can be applied to perform a probabilistic guarantee of soft tasks.The performance of the proposed method is compared with that of similar service mechanisms (dynamic realtime servers and proportional share schedulers) through extensive simulation experiments.
Hierarchical scheduling framework for virtual clustering of multiprocessors
, 2008
"... Scheduling of sporadic task systems on multiprocessor platforms is an area which has received much attention in the recent past. It is widely believed that finding an optimal scheduler is hard, and therefore most studies have focused on developing algorithms with good utilization bounds. These algor ..."
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Cited by 62 (5 self)
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Scheduling of sporadic task systems on multiprocessor platforms is an area which has received much attention in the recent past. It is widely believed that finding an optimal scheduler is hard, and therefore most studies have focused on developing algorithms with good utilization bounds. These algorithms can be broadly classified into two categories: partitioned scheduling in which tasks are statically assigned to individual processors, and global scheduling in which each task is allowed to execute on any processor in the platform. In this paper we consider a third, more general, approach called clusterbased scheduling. In this approach each task is statically assigned to a processor cluster, tasks in each cluster are globally scheduled among themselves, and clusters in turn are scheduled on the multiprocessor platform. We develop techniques to support such clusterbased scheduling algorithms, and also consider properties that minimize processor utilization of individual clusters. Since neither partitioned nor global strategies dominate over the other, clusterbased scheduling is a natural direction for research towards achieving improved utilization bounds. 1
Feasibility Problems for Recurring Tasks on One Processor
, 1992
"... We give a comprehensive summary of our recent research on the feasibility problems for various types of hardrealtime preemptive task systems on one processor. We include results on periodic, sporadic, and hybrid task systems. While many of the results herein have appeared elsewhere, this is the fi ..."
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Cited by 57 (10 self)
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We give a comprehensive summary of our recent research on the feasibility problems for various types of hardrealtime preemptive task systems on one processor. We include results on periodic, sporadic, and hybrid task systems. While many of the results herein have appeared elsewhere, this is the first paper presenting a holistic view of the entire problem.
An Event Stream Driven Approximation for the Analysis of RealTime Systems
 IEEE Proceedings of the 16th Euromicro Conference on RealTime Systems
, 2004
"... 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 so ..."
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Cited by 57 (9 self)
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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 contrary to earlier work, where the error depends on the different deadlines of the tasks, the error of our algorithm depends only on the capacity of the chosen processor. It guarantees the acceptances on a processor with slightly higher capacity than the unknown optimal processor. While the algorithm is scalable and the runtime depends on the chosen error, a tradeoff between running time and error is possible. 1.