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17
Mixed Pfair/ERfair Scheduling of Asynchronous Periodic Tasks
, 2001
"... Pfair Scheduling was proposed by... In this paper, we introduce a workconserving variant of Pfair scheduling called "earlyrelease" fair (ERfair) scheduling. We also present a new scheduling algorithm called PD² and show that it is optimal for scheduling any mix of earlyrelease and nonearly ..."
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Cited by 94 (44 self)
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Pfair Scheduling was proposed by... In this paper, we introduce a workconserving variant of Pfair scheduling called "earlyrelease" fair (ERfair) scheduling. We also present a new scheduling algorithm called PD² and show that it is optimal for scheduling any mix of earlyrelease and nonearlyrelease asynchronous, periodic tasks. In contrast, almost all prior work on Pfair scheduling has been limited to synchronous systems. PD²is an optimization of an earlier deadlinebased algorithm of Baruah, Gehrke, and Plaxton called PD; PD² uses a simpler tiebreaking scheme than PD to disambiguate equal deadlines. We present a series of counterexamples that suggest that, in general, the PD² tiebreaking mechanism cannot be simplified. In contrast to this, we show that no tiebreaking information is needed on twoprocessor systems.
Optimal RewardBased Scheduling of Periodic RealTime Tasks
, 1999
"... Rewardbased scheduling refers to the problem in which there is a reward associated with the execution of a task. In our framework, each realtime task comprises a mandatory and an optional part, with which a nondecreasing reward function is associated. Imprecise computation and IncreasedRewardwit ..."
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Cited by 63 (16 self)
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Rewardbased scheduling refers to the problem in which there is a reward associated with the execution of a task. In our framework, each realtime task comprises a mandatory and an optional part, with which a nondecreasing reward function is associated. Imprecise computation and IncreasedRewardwithIncreasedService models fall within the scope of this framework. In this paper, we address the rewardbased scheduling problem for periodic tasks. For linear and concave reward functions we show: (a) the existence of an optimal schedule where the optional service time of a task is constant at every instance and (b) how to efficiently compute this service time. We also prove that RMS (with harmonic periods), EDF and LLF policies are optimal when used with the optimal service times we computed, and that the problem becomes NPHard, when the reward functions are convex. Further, our solution eliminates runtime overhead, and makes possible the use of existing scheduling disciplines.
The Utilization Bounds of Partitioned and Pfair StaticPriority Scheduling on Multiprocessors Are 50%
"... This paper studies preemptive staticpriority scheduling on multiprocessors. We consider two approaches: global pfair staticpriority scheduling and partitioned traditional staticpriority scheduling. We prove that if presented algorithms are used and if less than 50% of the capacity is used then al ..."
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Cited by 29 (0 self)
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This paper studies preemptive staticpriority scheduling on multiprocessors. We consider two approaches: global pfair staticpriority scheduling and partitioned traditional staticpriority scheduling. We prove that if presented algorithms are used and if less than 50% of the capacity is used then all deadlines are met. It is known that no staticpriority multiprocessor scheduling algorithm can achieve a utilization bound greater than 50%.
On the Implementation of Pfairscheduled Multiprocessor Systems
, 2004
"... The goal of this dissertation is to extend the Pfair scheduling approach in order to enable its efficient implementation on a realtime multiprocessor. At present, Pfair scheduling is the only known means for optimally scheduling recurrent realtime tasks on multiprocessors. In
addition, there has b ..."
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Cited by 25 (12 self)
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The goal of this dissertation is to extend the Pfair scheduling approach in order to enable its efficient implementation on a realtime multiprocessor. At present, Pfair scheduling is the only known means for optimally scheduling recurrent realtime tasks on multiprocessors. In
addition, there has been growing practical interest in such approaches due to their fairness
guarantees. Unfortunately, prior work in this area has considered only the scheduling of
independent tasks, which do not communicate with each other or share resources. The work
presented herein focuses both on adding support for these actions and also on developing
techniques for reducing various forms of implementation overhead, including that produced
by task migrations and context switches. The thesis of this dissertation is:
tasks can be efficiently synchronized in Pfairscheduled systems and overhead due
to common system events, such as context switches and migrations, can be reduced.
This thesis is established through research in three areas. First, the preexisting Pfair schedul
ing theory is extended to support the scheduling of groups of tasks as a single entity. Second,
mechanisms for supporting both lockbased and lockfree synchronization are presented. Lock
based synchronization coordinates access to shared resources through the use of semaphores.
On the other hand, lockfree operations are optimistically attempted and then retried if the
operation fails. Last, the deployment of Pfair scheduling on a symmetric multiprocessor is
considered.
Efficient and Flexible Fair Scheduling of Realtime Tasks on Multiprocessors
 University
, 2003
"... ..."
A New Look at Pfair Priorities
 In Submission
, 1999
"... We consider Pfair scheduling in realtime multiprocessor systems. Under Pfair scheduling, tasks are required to execute at steady rates. The most efficient Pfair scheduling algorithm proposed to date is an algorithm called PD developed by Baruah and colleagues. PD schedules periodic tasks by breakin ..."
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Cited by 16 (3 self)
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We consider Pfair scheduling in realtime multiprocessor systems. Under Pfair scheduling, tasks are required to execute at steady rates. The most efficient Pfair scheduling algorithm proposed to date is an algorithm called PD developed by Baruah and colleagues. PD schedules periodic tasks by breaking them into quantumlength subtasks that are subject to intermediate deadlines. Ties among subtasks with the same intermediate deadline are broken by inspecting four tiebreak parameters. PD improved upon a previous algorithm called PF, which relies on a lessefficient procedure for resolving ties. In this paper, we show that the priority definition used in PD can be simplified to consist of one intermediate deadline and only two tiebreak parameters. We also show that further simplifications are, in general, unlikely. In particular, we show if either tiebreak parameter is eliminated, then there exists a feasible task set that is not correctly scheduled. Although both tiebreaks are needed ...
StaticPriority Periodic Scheduling on Multiprocessors
 In Proceedings of the 21st IEEE RealTime Systems Symposium
, 2000
"... We present a new sufficient condition for the schedulability of preemptable, periodic, hardrealtime task sets using the very simple staticpriority weightmonotonic scheduling scheme. Like a previous condition due to Baruah et al., our condition actually determines pfair schedulability. Pfairness ..."
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Cited by 11 (0 self)
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We present a new sufficient condition for the schedulability of preemptable, periodic, hardrealtime task sets using the very simple staticpriority weightmonotonic scheduling scheme. Like a previous condition due to Baruah et al., our condition actually determines pfair schedulability. Pfairness requires that the schedule, in addition to being periodic, schedules each task at an approximately even rate. Our condition improves on the previous one in two important ways. First, it can determine that task sets with high utilization and many tasks are schedulable, while the previous condition cannot. Second, our condition applies to both uniprocessors and multiprocessors, while the previous condition applies only to uniprocessors. We present simulations that show that our condition is highly accurate for many cases of interest. 1 Introduction Schedulability of periodic, preemptable, hard realtime tasks on uniprocessors under staticpriority schemes such as ratemonotonic and deadlinem...
Adaptive Dissemination of Data in TimeCritical Asymmetric Communication Environments
, 1999
"... The proliferation of new dataintensive applications in asymmetric communication environments has led to an increasing interest in the development of pushbased techniques, in which the information is broadcast to a large population of clients in order to achieve the most efficient use of the limite ..."
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Cited by 11 (0 self)
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The proliferation of new dataintensive applications in asymmetric communication environments has led to an increasing interest in the development of pushbased techniques, in which the information is broadcast to a large population of clients in order to achieve the most efficient use of the limited server and communication resources. It is important to note that quite often the data that is broadcast is timecritical in nature. Most of the related current research focuses on a pure pushbased approach (Broadcast Disks model), where the transmission of data is done without allowing explicit requests from the users. More recently, some bidirectional models incorporating a lowcapacity uplink channel have been proposed in order to increase the functionality of the Broadcast Disks model. However, the impact of integration of the uplink channel has been investigated using only static client profiles or ignoring the existence of timing constraints associated with data. None of the existing...
A schedulable utilization bound for the multiprocessor EPDF Pfair algorithm
 RealTime Systems
, 2008
"... The earliestpseudodeadlinefirst (EPDF) Pfair scheduling algorithm is less expensive than some other known Pfair algorithms, but is not optimal for scheduling recurrent realtime tasks on more than two processors. In prior work, sufficient pertask weight (i.e., utilization) restrictions were esta ..."
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Cited by 3 (0 self)
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The earliestpseudodeadlinefirst (EPDF) Pfair scheduling algorithm is less expensive than some other known Pfair algorithms, but is not optimal for scheduling recurrent realtime tasks on more than two processors. In prior work, sufficient pertask weight (i.e., utilization) restrictions were established for ensuring that tasks either do not miss their deadlines or have bounded tardiness when scheduled under EPDF. Implicit in these restrictions is the assumption that the total system utilization may equal the total available processing capacity (i.e., the total number of processors). This paper considers an orthogonal issue, namely, determining a sufficient restriction on the total utilization of a task set for it to be schedulable (i.e., a schedulable utilization bound) under EPDF, assuming that there are no pertask weight restrictions. We prove that a task set with total utilization at most 3M+1 4 is correctly scheduled under EPDF on M processors, regardless of how large each task’s weight is. At present, we do not know whether this value represents the worstcase for EPDF, but we do provide a counterexample that shows that it cannot be improved to exceed 86 % of the total processing capacity. The schedulable utilization bound we derive is expressed in terms of the maximum weight of any task, and hence, if this value is known, may be used to schedule task sets with total utilization greater than 3M+1
Nonpreemptive multiprocessor static scheduling for systems with precedence and strict periodicity constraints
 In Proceedings of the 10th International Workshop On Project Management and Scheduling, PMS’06, Posnan
, 2006
"... strict periodicity constraints ..."