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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.
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.
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
A novel Task Scheduling in Multiprocessor Systems with Genetic Algorithm by using Elitism stepping method
, 2008
"... Abstract. Task scheduling is essential for the suitable operation of multiprocessor systems. The aim of task scheduling is to determine an assignment of tasks to processors for shortening the length of schedules. The problem of task scheduling on multiprocessor systems is known to be NPcomplete in ..."
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Cited by 3 (0 self)
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Abstract. Task scheduling is essential for the suitable operation of multiprocessor systems. The aim of task scheduling is to determine an assignment of tasks to processors for shortening the length of schedules. The problem of task scheduling on multiprocessor systems is known to be NPcomplete in general. Solving this problem using by conventional techniques needs reasonable amounts of time. Therefore, many heuristic techniques were introduced for solving it. This paper presents a new heuristic algorithm for task scheduling, based on evolutionary method which embeds a new fast technique named Elitism Stepping into Genetic Algorithm (GA). By comparing the proposed algorithm with an existing GAbased algorithm, it is found that the computation time of the new algorithm to find a suboptimal schedule is decreased; however, the length of schedule or the finish time is decreased too.
Fair Scheduling of Realtime Tasks on Multiprocessors
 Handbook of Scheduling
, 2005
"... There has been much recent interest in fair scheduling algorithms for realtime multiprocessor systems. The roots of much of the research on this topic can be traced back to the seminal work of Baruah et al. on Proportionate fairness (Pfairness) [6]. This work proved that the problem of optimally sc ..."
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Cited by 2 (0 self)
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There has been much recent interest in fair scheduling algorithms for realtime multiprocessor systems. The roots of much of the research on this topic can be traced back to the seminal work of Baruah et al. on Proportionate fairness (Pfairness) [6]. This work proved that the problem of optimally scheduling periodic tasks on multiprocessors could be solved online in polynomial time by using Pfair scheduling algorithms. Pfair scheduling differs from more conventional realtime scheduling approaches in that tasks are explicitly required to execute at steady rates. In most realtime scheduling disciplines, the notion of a rate is implicit. For example, in a periodic schedule, a task T executes at a rate defined by its required utilization (T.e/T.p) over large intervals. However, T's execution rate over short intervals, e.g., individual periods, may vary significantly. Hence, the notion of a rate under the periodic task model is a bit inexact. Under Pfair scheduling, each task is executed...