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114
Quickrelease Fair Scheduling
 In Proceedings of the 12th Euromicro Conference on RealTime Systems
, 2003
"... In prior work on multiprocessor fairness, efficient techniques with provable properties for reallocating spare processing capacity have been elusive. In this paper, we address this shortcoming by proposing a new notion of multiprocessor fairness, called quickrelease fair (QRfair) scheduling, which ..."
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Cited by 98 (37 self)
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In prior work on multiprocessor fairness, efficient techniques with provable properties for reallocating spare processing capacity have been elusive. In this paper, we address this shortcoming by proposing a new notion of multiprocessor fairness, called quickrelease fair (QRfair) scheduling, which is a derivative of Pfair scheduling that allows efficient allocation of spare capacity. Under QRfair scheduling, each task is specified by giving both a minimum and a maximum weight (i.e., processor share). The goal is to schedule each task (as the available spare capacity changes) at a rate that is (i) at least that implied by its minimum weight and (ii) at most that implied by its maximum weight. Our contributions are fourfold. First, we present a quickrelease variant of the PD Pfair scheduling algorithm called PD . Second, we formally prove that the allocations of PD always satisfy (i) and (ii). Third, we consider the problem of defining maximum weights in a way that encourages a fair distribution of spare capacity. Fourth, we present results from extensive simulation experiments that show the efficacy of PD in allocating spare capacity.
Improved schedulability analysis of EDF on multiprocessor platforms
 In Proc. of the 17th Euromicro Conf. on RealTime Sys
, 2005
"... Multiprocessor hardware platforms are now being considered for embedded systems, due to their high computational power and little additional cost when compared to single processor systems. When scheduling realtime applications on multiprocessor platforms, a possibility is to use global scheduling, ..."
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Cited by 85 (3 self)
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Multiprocessor hardware platforms are now being considered for embedded systems, due to their high computational power and little additional cost when compared to single processor systems. When scheduling realtime applications on multiprocessor platforms, a possibility is to use global scheduling, where a scheduling algorithm dynamically assign tasks to processors, and tasks can migrate from one processor to another during their execution. In this paper, we tackle the problem of schedulability analysis of sporadic tasks in global scheduling systems, where the scheduler is the Earliest Deadline First (EDF) algorithm. We provide two main contributions. First, we show that two recently proposed tests perform poorly when the task set contains heavy tasks (i.e. tasks with high utilization). We also show that neither test dominates the other. As a second contribution, we introduce a new schedulability test that improves significantly the percentage of accepted task sets, especially when considering task sets containing heavy tasks. We show the effectiveness of the proposed test through an extensive set of experiments. 1.
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 85 (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.
Optimal Ratebased Scheduling on Multiprocessors
 In Proceedings of the 34th ACM Symposium on Theory of Computing
, 2001
"... We consider the intrasporadic task model, which is a generalization of the sporadic task model motivated by recent work on Pfair scheduling. The intrasporadic model is essentially a quantumbased, multiprocessor variant of the uniprocessor ratebased execution model of Jeffay and Goddard. In the i ..."
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Cited by 83 (41 self)
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We consider the intrasporadic task model, which is a generalization of the sporadic task model motivated by recent work on Pfair scheduling. The intrasporadic model is essentially a quantumbased, multiprocessor variant of the uniprocessor ratebased execution model of Jeffay and Goddard. In the intrasporadic model, a task is specified by an average rate of execution, and there is no restriction on instantaneous execution rates. Such exibility is useful in applications in which some processing steps may be highly jittered. In previous work, we showed that an intrasporadic task system is feasible on M processors i its total utilization is at most M . We also gave an optimal algorithm for scheduling intrasporadic tasks on two processors. In this paper, we show that the PD&sup2; Pfair algorithm can be used to schedule any intrasporadic task system that is feasible on M processors. Because the sporadic model is a special case of the intrasporadic model, our work shows that PD&sup2; is also optimal for scheduling sporadic tasks on a multiprocessor. This paper is the first to show that sporadic or intrasporadic tasks can be optimally scheduled on systems of more than two processors.
Schedulability analysis of global scheduling algorithms on multiprocessor platforms
, 2008
"... ..."
A flexible realtime locking protocol for multiprocessors
 IN PROCEEDINGS OF THE 13TH IEEE INTERNATIONAL CONFERENCE ON EMBEDDED AND REALTIME COMPUTING SYSTEMS AND APPLICATIONS
, 2007
"... Realtime scheduling algorithms for multiprocessor systems have been the subject of considerable recent interest. For such an algorithm to be truly useful in practice, support for semaphorebased locking must be provided. However, for many global scheduling algorithms, no such mechanisms have been p ..."
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Cited by 62 (33 self)
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Realtime scheduling algorithms for multiprocessor systems have been the subject of considerable recent interest. For such an algorithm to be truly useful in practice, support for semaphorebased locking must be provided. However, for many global scheduling algorithms, no such mechanisms have been proposed. Furthermore, in the partitioned case, most prior semaphore schemes are either inefficient or restrict critical sections considerably. In this paper, a new flexible multiprocessor locking scheme is presented that can be applied under both partitioning and global scheduling. This scheme allows unrestricted criticalsection nesting, but has been designed to deal with the common case of short nonnested accesses efficiently.
Tardiness bounds under global edf scheduling on a multiprocessor
 In RTSS ’05: Proceedings of the 26th IEEE International RealTime Systems Symposium
, 2005
"... This paper considers the scheduling of soft realtime sporadic task systems under global EDF on an identical multiprocessor. Though Pfair scheduling is theoretically optimal for hard realtime task systems on multiprocessors, it can incur signicant runtime overhead. Hence, other scheduling algorit ..."
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Cited by 60 (38 self)
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This paper considers the scheduling of soft realtime sporadic task systems under global EDF on an identical multiprocessor. Though Pfair scheduling is theoretically optimal for hard realtime task systems on multiprocessors, it can incur signicant runtime overhead. Hence, other scheduling algorithms that are not optimal, including EDF, have continued to receive considerable attention. However, prior research on such algorithms has focussed mostly on hard realtime systems, where, to ensure that all deadlines are met, approximately 50 % of the available processing capacity will have to be sacriced in the worst case. This may be overkill for soft realtime systems that can tolerate deadline misses by bounded amounts (i.e., bounded tardiness). In this paper, we derive tardiness bounds under preemptive and nonpreemptive global EDF on multiprocessors when the total utilization of a task system is not restricted and may equal the number of processors. Our tardiness bounds depend on pertask utilizations and execution costs the lower these values, the lower the tardiness bounds. As a nal remark, we note that global EDF may be superior to partitioned EDF for multiprocessorbased soft realtime systems in that the latter does not offer any scope to improve system utilization even if bounded tardiness can be tolerated. ¤Work supported by NSF grants CCR 0204312, CCR 0309825, and CCR 0408996. The rst author was also supported by an IBM Ph.D. fellowship.
Multiprocessor Scheduling with Few Preemptions
 IPP Hurray Research Group, Polytechnic Institute of Porto, Portugal HURRAYTR060811, Available at http://www.hurray.isep.ipp.pt/privfiles/trhurray060811.pdf
, 2006
"... Consider the problem of scheduling a set of periodically arriving tasks on a multiprocessor with the 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 % a ..."
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Cited by 53 (5 self)
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Consider the problem of scheduling a set of periodically arriving tasks on a multiprocessor with the 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 preemption and in doing so it has a utilization bound of 100%.
Efficient scheduling of soft realtime applications on multiprocessors
 In Proceedings of the 15th Euromicro Conference on Realtime Systems
, 2003
"... In soft realtime applications, tasks are allowed to miss their deadlines. Thus, lesscostly scheduling algorithms can be used at the price of occasional violations of timing constraints. This may be acceptable if reasonable tardiness bounds (i.e., bounds on the extent to which deadlines may be miss ..."
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Cited by 48 (20 self)
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In soft realtime applications, tasks are allowed to miss their deadlines. Thus, lesscostly scheduling algorithms can be used at the price of occasional violations of timing constraints. This may be acceptable if reasonable tardiness bounds (i.e., bounds on the extent to which deadlines may be missed) can be guaranteed. In this paper, we consider soft realtime applications implemented on multiprocessors. Pfair scheduling algorithms are the only known means of optimally scheduling hard realtime applications on multiprocessors. For this reason, we consider the use of such algorithms here. In the design of Pfair scheduling algorithms, devising schemes to correctly break ties when several tasks have the same deadline is a critical issue. Such tiebreaking schemes entail overhead that may be unacceptable or unnecessary in soft realtime applications. In this paper, we consider the earliest pseudodeadline first (EPDF) Pfair algorithm, which avoids this overhead by using no tiebreaking information. Our main contributions are twofold. First, we establish a condition for ensuring a tardiness of at most one quantum under EPDF. This condition is very liberal and should often hold in practice. Second, we present simulation results involving randomlygenerated task sets, including those that do not satisfy our condition. In these experiments, deadline misses rarely occurred, and no misses by more than one quantum ever occurred. ∗ Work supported by NSF grants CCR 9972211, CCR 9988327, ITR 0082866, and CCR 0204312. 1
On the Scalability of RealTime Scheduling Algorithms on Multicore Platforms: A Case Study
, 2008
"... Multicore platforms are predicted to become significantly larger in the coming years. Given that realtime workloads will inevitably be deployed on such platforms, the scalability of the scheduling algorithms used to support such workloads warrants investigation. In this paper, this issue is conside ..."
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Cited by 44 (13 self)
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Multicore platforms are predicted to become significantly larger in the coming years. Given that realtime workloads will inevitably be deployed on such platforms, the scalability of the scheduling algorithms used to support such workloads warrants investigation. In this paper, this issue is considered and an empirical evaluation of several global and partitioned scheduling algorithms is presented. This evaluation was conducted using a Sun Niagara multicore platform with 32 logical CPUs (eight cores, four hardware threads per core). In this study, each tested algorithm proved to be a viable choice for some subset of the workload categories considered.