Fine-Grained Task Reweighting on Multiprocessors

Block, Aaron; Anderson, James H.; Bishop, Gary

doi:10.1109/rtcsa.2005.53

Cited by 18 publications

(17 citation statements)

References 12 publications

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“…We now introduce two new reweighting rules that are CNG-EDF extensions of the PD 2 -OF reweighting rules presented by us previously [3]. As mentioned before, these rules work by modifying future job release times and deadlines.…”

Section: Task Reweightingmentioning

confidence: 99%

“…Inset (a) depicts a CNG-EDF schedule and insets (b) depicts T 's SW schedule. Notice that in the SW schedule T 1 does not receive any allocations over the interval [3,6). This is because at time 3 the total allocation to T is released, and therefore T 1 has an incomplete job with a scheduling weight of 1/2.…”

Section: Tardiness and Lagmentioning

confidence: 99%

“…3(c). Notice that, over the range [3,6), the task T 1 receives allocations equal to its weight at every instant. Compare this to the SW schedule (inset (b)), in which T 1 receives no allocations over the range [3,6).…”

Section: Driftmentioning

confidence: 99%

“…Accuracy is assessed in terms of three quantities, "drift," "overload error," and "tardiness," which are measured in terms of the system's scheduling quantum size. Drift is the error, in comparison to an ideal allocation, that results due to a reweighting event [3]. (Under an ideal allocation, tasks are reweighted instantaneously, which is not possible in practice.)…”

mentioning

confidence: 99%

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Task reweighting under global scheduling on multiprocessors

2007

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We consider schemes for enacting task share changes-a process called reweighting-on real-time multiprocessor platforms. Our particular focus is reweighting schemes that are deployed in environments in which tasks may frequently request significant share changes. Prior work has shown that fair scheduling algorithms are capable of reweighting tasks with minimal allocation error and that partitioning-based scheduling algorithms can reweight tasks with better average-case performance, but greater error. However, preemption and migration overheads can be high in fair schemes. In this paper, we consider the question of whether global scheduling techniques can improve the accuracy of reweighting relative to partitioning-based schemes and provide improved average-case performance relative to fair scheduled systems. Our conclusion is that, for soft real-time systems, global scheduling techniques provide a good mix of accuracy and average-case performance.

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Section: Task Reweightingmentioning

confidence: 99%

Section: Tardiness and Lagmentioning

confidence: 99%

Section: Driftmentioning

confidence: 99%

mentioning

confidence: 99%

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Task reweighting under global scheduling on multiprocessors

2007

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“…In addition, recent work [Block et al 2005] on "fine-grained" reweighting techniques for Pfair scheduling shows considerable improvement over existing techniques. Unfortunately, due to significant differences between the system model considered in [Block et al 2005] and that considered here, it is unclear whether fine-grained reweighting (or the concepts underlying it) can be used to produce an effective dynamic-weight locking protocol for hard real-time systems.…”

Section: Problemsmentioning

confidence: 99%

Locking under Pfair scheduling

Holman

Anderson

2006

ACM Trans. Comput. Syst.

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We present several locking synchronization protocols for Pfair-scheduled multiprocessor systems. We focus on two classes of protocols. The first class is only applicable in systems in which all critical sections are short relative to the length of the scheduling quantum. In this case, efficient synchronization can be achieved by ensuring that all locks have been released before tasks are preempted. This is accomplished by exploiting the quantum-based nature of Pfair scheduling, which provides a priori knowledge of all possible preemption points. The second and more general protocol class is applicable to any system. For this class, we consider the use of a client-server model. We also discuss the viability of inheritance-based protocols in Pfair-scheduled systems.

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A schedulable utilization bound for the multiprocessor $\mathsf{EPDF}$ Pfair algorithm

Devi

Anderson

2007

Real-Time Syst

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The earliest-pseudo-deadline-first (EPDF) Pfair scheduling algorithm is less expensive than some other known Pfair algorithms, but is not optimal for scheduling recurrent real-time tasks on more than two processors. In prior work, sufficient per-task 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 per-task 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 worst-case 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 4 .

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Fine-Grained Task Reweighting on Multiprocessors

Cited by 18 publications

References 12 publications

Task reweighting under global scheduling on multiprocessors

Task reweighting under global scheduling on multiprocessors

Locking under Pfair scheduling

A schedulable utilization bound for the multiprocessor $\mathsf{EPDF}$ Pfair algorithm

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