Shelby Funk | The University of Georgia (original) (raw)

Papers by Shelby Funk

Large introductory-level classes provide a cost-efficient approach for universities to serve many... more Large introductory-level classes provide a cost-efficient approach for universities to serve many students at once, but also present several challenges to learning (e.g., poor visual angles). In addition, more students with declared, undeclared, or undiagnosed learning disabilities are entering the college and university systems. In the spirit of universal design, we created a group note-taking system in our large introductory

Scheduling real-time systems on multiprocessors introduces complexities that do not arise when us... more Scheduling real-time systems on multiprocessors introduces complexities that do not arise when using uniprocessors. When scheduling using EDF on multiprocessor platforms, breaking deadline ties in different ways can change the resulting schedule dramatically. We consider methods to resolve the ambiguities in EDF priorities due to coincident deadlines. We show that no optimal ambiguity solver can be online. We also show that no optimal static tiebreaker exists even if we relax the on-line property.

The partitioning of periodic task systems upon uniform multiprocessors is considered. In the part... more The partitioning of periodic task systems upon uniform multiprocessors is considered. In the partitioned approach to scheduling periodic tasks upon multiprocessors, each task is assigned to a specific processor and all jobs generated by a task are required to execute upon the processor to which the task is assigned. A uniform heterogeneous multiprocessor is a multiprocessor in which each processor has an associated speed -a processor of speed s operating for t units of time will perform s × t units of work. Partitioning of periodic task systems requires solving the bin-packing problem, which is known to be intractable (NP-hard in the strong sense). This paper presents methods for finding an approximate utilization bound for partitioned scheduling on uniform heterogeneous multiprocessors.

Technique Et Science Informatiques, 2005

Restricted migration of periodic and sporadic tasks on uniform heterogeneous multiprocessors is c... more Restricted migration of periodic and sporadic tasks on uniform heterogeneous multiprocessors is considered. Migration between different processors of a multiprocessor causes overhead that may be prohibitively high for real-time systems, where accurate timing is essential. ...

Page 1. Task assignment in heterogeneous multiprocessor platforms ∗ Sanjoy K. BaruahShelby Funk T... more Page 1. Task assignment in heterogeneous multiprocessor platforms ∗ Sanjoy K. BaruahShelby Funk The University of North Carolina Abstract In the partitioned approach to scheduling periodic tasks upon multiprocessors, each task is ...

Scheduling real-time systems on multiprocessors introduces complexities that do not arise when us... more Scheduling real-time systems on multiprocessors introduces complexities that do not arise when using uniprocessors. If the processors do not all operate at the same speed, scheduling becomes even more complex. When scheduling using EDF on multiprocessors, breaking deadline ties in different ways can change the resulting schedule dramatically. We consider methods to resolve the ambiguities in EDF priorities due to coincident deadlines. We show that no optimal ambiguity resolver can be both on-line and priority-driven. When processor speeds differ, a job's minimum required execution rate may also be considered in the scheduling decisions. We propose a modification of existing scheduling algorithms that considers processor speed and minimum required execution rate. We show that the resulting algorithm dominates EDF on identical multiprocessors and conjecture that it dominates EDF on uniform multiprocessors as well.

IEEE Transactions on Computers, 2003

Each processor in a uniform multiprocessor machine is characterized by a speed or computing capac... more Each processor in a uniform multiprocessor machine is characterized by a speed or computing capacity, with the interpretation that a job executing on a processor with speed s for t time units completes ðs  tÞ units of execution. The earliestdeadline-first (EDF) scheduling of hard-real-time systems upon uniform multiprocessor machines is considered. It is known that online algorithms tend to perform very poorly in scheduling such hard-real-time systems on multiprocessors; resource-augmentation techniques are presented here that permit online algorithms in general (EDF in particular) to perform better than may be expected given these inherent limitations. It is shown that EDF scheduling upon uniform multiprocessors is robust with respect to both job execution requirements and processor computing capacity.

In hard-real-time (HRT) systems, there are certain basic units of work, known as jobs, which must... more In hard-real-time (HRT) systems, there are certain basic units of work, known as jobs, which must be executed in a timely manner. In one popular model of hard-real-time systems, each job is assumed to be characterized by three parameters - an arrival time, an execution ...

Restricted migration of periodic and sporadic tasks on uniform multiprocessors is considered. On ... more Restricted migration of periodic and sporadic tasks on uniform multiprocessors is considered. On multiprocessors, job migration can cause a prohibitively high overhead — particularly in real-time systems where accurate timing is essential. However, if periodic tasks do not ...

We consider the problem of optimal real-time scheduling of periodic and sporadic tasks for identi... more We consider the problem of optimal real-time scheduling of periodic and sporadic tasks for identical multiprocessors. A number of recent papers have used the notions of fluid scheduling and deadline partitioning to guarantee optimality and improve performance. In this paper, we develop a unifying theory with the DP-FAIR scheduling policy and examine how it overcomes problems faced by greedy scheduling algorithms. We then present a simple DP-FAIR scheduling algorithm, DP-WRAP, which serves as a least common ancestor to many recent algorithms. We also show how to extend DP-FAIR to the scheduling of sporadic tasks with arbitrary deadlines.

Computing Research Repository, 2010

Abstract This research addresses the multiprocessor scheduling problem of hard real-time systems,... more Abstract This research addresses the multiprocessor scheduling problem of hard real-time systems, and it especially focuses on optimal and global schedulers when practical constraints are taken into account. First, we propose an improvement of the optimal algorithm BF. We ...

A note on task-parallelism upon multiprocessors Joël Goossens Université Libre de Bruxelles Bruss... more A note on task-parallelism upon multiprocessors Joël Goossens Université Libre de Bruxelles Brussels, Belgium Email: joel. goossens@ ulb. ac. be Shelby Funk University of Georgia Athens, GA, USA Email: shelby@ cs. uga. edu We consider the scheduling of arbitrary ...

This paper introduces a new model for describing jobs and tasks for real-time systems. Using this... more This paper introduces a new model for describing jobs and tasks for real-time systems. Using this model can improve utilization bounds on uniform multiprocessors, in which each processor has an associated speed. Traditionally, a job executing on a processor of speed s for t units of time will perform s × t units of work. However, this uniform scaling only occurs if tasks are completely CPU bound. In practice, tasks will have some portion of execution that does not scale with the increased CPU speed. Dividing the execution into CPU execution and fixed execution allows the scheduler to place CPU bound tasks on faster processors, as they can take full advantage of the extra speed. This model is used in a new utilization test for EDF scheduling with restricted migration, r-EDF, in which tasks are allowed to migrate, but only at job boundaries. The test is proven to be better than the existing r-EDF test for uniform multiprocessors.

This paper presents feasibility tests for scheduling instances of real-time jobs on uniform multi... more This paper presents feasibility tests for scheduling instances of real-time jobs on uniform multiprocessor platforms. In a uniform multiprocessor, each processor has an associated speed -a job executing on a processor of speed s for t time units performs s × t units of work. Two feasibility tests are presented. First, a sufficient condition is presented -whenever this condition holds the jobs are known to be feasible on the multiprocessor. Then, a necessary condition is presented -whenever the jobs are feasible on the multiprocessor, this condition must hold.

The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizat... more The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizationbased conditions are derived for determining whether a periodic task system meets all deadlines when scheduled using the earliest deadline ®rst scheduling algorithm (EDF) upon a given multiprocessor platform. A new priority-driven algorithm is proposed for scheduling periodic task systems upon multiprocessor platforms: this algorithm is shown to successfully schedule some task systems for which EDF may fail to meet all deadlines.

In uniform multiprocessor platforms, the various proces-sors comprising the multiprocessor platfo... more In uniform multiprocessor platforms, the various proces-sors comprising the multiprocessor platform may have dif-ferent computing capacities. The focus of this paper is the design of efficient tests for determining whether the Earliest Deadline First Scheduling Algorithm (EDF) can ...

Real-time multiprocessor systems are now commonplace. Designs range from single-chip architecture... more Real-time multiprocessor systems are now commonplace. Designs range from single-chip architectures, with a modest number of processors, to large-scale signal-processing systems, such as synthetic-aperture radar systems. For uniprocessor systems, the problem of ensuring that deadline constraints are met has been widely studied: effective scheduling algorithms that take into account the many complexities that arise in real systems (e.g., synchronization costs, system overheads, etc.) are well understood. In contrast, researchers are just beginning to understand the trade-offs that exist in multiprocessor systems. In this chapter, we analyze the trade-offs involved in scheduling independent, periodic real-time tasks on a multiprocessor.

Real-time Systems, 2003

The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizat... more The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilization-based conditions are derived for determining whether a periodic task system meets all deadlines when scheduled using the earliest deadline first scheduling algorithm (EDF) upon a given multiprocessor platform. A new priority-driven algorithm is proposed for scheduling periodic task systems upon multiprocessor platforms: this algorithm is shown to successfully schedule some task systems for which EDF may fail to meet all deadlines.

We have recently been studying the scheduling of real-time systems uponuniform and identical mult... more We have recently been studying the scheduling of real-time systems uponuniform and identical multiprocessor platforms. In particular, we have beenexploring the use of EDF-scheduling in such systems; this paper summarizessome of our recent ndings in this eld.

Large introductory-level classes provide a cost-efficient approach for universities to serve many... more Large introductory-level classes provide a cost-efficient approach for universities to serve many students at once, but also present several challenges to learning (e.g., poor visual angles). In addition, more students with declared, undeclared, or undiagnosed learning disabilities are entering the college and university systems. In the spirit of universal design, we created a group note-taking system in our large introductory

Scheduling real-time systems on multiprocessors introduces complexities that do not arise when us... more Scheduling real-time systems on multiprocessors introduces complexities that do not arise when using uniprocessors. When scheduling using EDF on multiprocessor platforms, breaking deadline ties in different ways can change the resulting schedule dramatically. We consider methods to resolve the ambiguities in EDF priorities due to coincident deadlines. We show that no optimal ambiguity solver can be online. We also show that no optimal static tiebreaker exists even if we relax the on-line property.

The partitioning of periodic task systems upon uniform multiprocessors is considered. In the part... more The partitioning of periodic task systems upon uniform multiprocessors is considered. In the partitioned approach to scheduling periodic tasks upon multiprocessors, each task is assigned to a specific processor and all jobs generated by a task are required to execute upon the processor to which the task is assigned. A uniform heterogeneous multiprocessor is a multiprocessor in which each processor has an associated speed -a processor of speed s operating for t units of time will perform s × t units of work. Partitioning of periodic task systems requires solving the bin-packing problem, which is known to be intractable (NP-hard in the strong sense). This paper presents methods for finding an approximate utilization bound for partitioned scheduling on uniform heterogeneous multiprocessors.

Technique Et Science Informatiques, 2005

Restricted migration of periodic and sporadic tasks on uniform heterogeneous multiprocessors is c... more Restricted migration of periodic and sporadic tasks on uniform heterogeneous multiprocessors is considered. Migration between different processors of a multiprocessor causes overhead that may be prohibitively high for real-time systems, where accurate timing is essential. ...

Page 1. Task assignment in heterogeneous multiprocessor platforms ∗ Sanjoy K. BaruahShelby Funk T... more Page 1. Task assignment in heterogeneous multiprocessor platforms ∗ Sanjoy K. BaruahShelby Funk The University of North Carolina Abstract In the partitioned approach to scheduling periodic tasks upon multiprocessors, each task is ...

Scheduling real-time systems on multiprocessors introduces complexities that do not arise when us... more Scheduling real-time systems on multiprocessors introduces complexities that do not arise when using uniprocessors. If the processors do not all operate at the same speed, scheduling becomes even more complex. When scheduling using EDF on multiprocessors, breaking deadline ties in different ways can change the resulting schedule dramatically. We consider methods to resolve the ambiguities in EDF priorities due to coincident deadlines. We show that no optimal ambiguity resolver can be both on-line and priority-driven. When processor speeds differ, a job's minimum required execution rate may also be considered in the scheduling decisions. We propose a modification of existing scheduling algorithms that considers processor speed and minimum required execution rate. We show that the resulting algorithm dominates EDF on identical multiprocessors and conjecture that it dominates EDF on uniform multiprocessors as well.

IEEE Transactions on Computers, 2003

Each processor in a uniform multiprocessor machine is characterized by a speed or computing capac... more Each processor in a uniform multiprocessor machine is characterized by a speed or computing capacity, with the interpretation that a job executing on a processor with speed s for t time units completes ðs  tÞ units of execution. The earliestdeadline-first (EDF) scheduling of hard-real-time systems upon uniform multiprocessor machines is considered. It is known that online algorithms tend to perform very poorly in scheduling such hard-real-time systems on multiprocessors; resource-augmentation techniques are presented here that permit online algorithms in general (EDF in particular) to perform better than may be expected given these inherent limitations. It is shown that EDF scheduling upon uniform multiprocessors is robust with respect to both job execution requirements and processor computing capacity.

In hard-real-time (HRT) systems, there are certain basic units of work, known as jobs, which must... more In hard-real-time (HRT) systems, there are certain basic units of work, known as jobs, which must be executed in a timely manner. In one popular model of hard-real-time systems, each job is assumed to be characterized by three parameters - an arrival time, an execution ...

Restricted migration of periodic and sporadic tasks on uniform multiprocessors is considered. On ... more Restricted migration of periodic and sporadic tasks on uniform multiprocessors is considered. On multiprocessors, job migration can cause a prohibitively high overhead — particularly in real-time systems where accurate timing is essential. However, if periodic tasks do not ...

We consider the problem of optimal real-time scheduling of periodic and sporadic tasks for identi... more We consider the problem of optimal real-time scheduling of periodic and sporadic tasks for identical multiprocessors. A number of recent papers have used the notions of fluid scheduling and deadline partitioning to guarantee optimality and improve performance. In this paper, we develop a unifying theory with the DP-FAIR scheduling policy and examine how it overcomes problems faced by greedy scheduling algorithms. We then present a simple DP-FAIR scheduling algorithm, DP-WRAP, which serves as a least common ancestor to many recent algorithms. We also show how to extend DP-FAIR to the scheduling of sporadic tasks with arbitrary deadlines.

Computing Research Repository, 2010

Abstract This research addresses the multiprocessor scheduling problem of hard real-time systems,... more Abstract This research addresses the multiprocessor scheduling problem of hard real-time systems, and it especially focuses on optimal and global schedulers when practical constraints are taken into account. First, we propose an improvement of the optimal algorithm BF. We ...

A note on task-parallelism upon multiprocessors Joël Goossens Université Libre de Bruxelles Bruss... more A note on task-parallelism upon multiprocessors Joël Goossens Université Libre de Bruxelles Brussels, Belgium Email: joel. goossens@ ulb. ac. be Shelby Funk University of Georgia Athens, GA, USA Email: shelby@ cs. uga. edu We consider the scheduling of arbitrary ...

This paper introduces a new model for describing jobs and tasks for real-time systems. Using this... more This paper introduces a new model for describing jobs and tasks for real-time systems. Using this model can improve utilization bounds on uniform multiprocessors, in which each processor has an associated speed. Traditionally, a job executing on a processor of speed s for t units of time will perform s × t units of work. However, this uniform scaling only occurs if tasks are completely CPU bound. In practice, tasks will have some portion of execution that does not scale with the increased CPU speed. Dividing the execution into CPU execution and fixed execution allows the scheduler to place CPU bound tasks on faster processors, as they can take full advantage of the extra speed. This model is used in a new utilization test for EDF scheduling with restricted migration, r-EDF, in which tasks are allowed to migrate, but only at job boundaries. The test is proven to be better than the existing r-EDF test for uniform multiprocessors.

This paper presents feasibility tests for scheduling instances of real-time jobs on uniform multi... more This paper presents feasibility tests for scheduling instances of real-time jobs on uniform multiprocessor platforms. In a uniform multiprocessor, each processor has an associated speed -a job executing on a processor of speed s for t time units performs s × t units of work. Two feasibility tests are presented. First, a sufficient condition is presented -whenever this condition holds the jobs are known to be feasible on the multiprocessor. Then, a necessary condition is presented -whenever the jobs are feasible on the multiprocessor, this condition must hold.

The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizat... more The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizationbased conditions are derived for determining whether a periodic task system meets all deadlines when scheduled using the earliest deadline ®rst scheduling algorithm (EDF) upon a given multiprocessor platform. A new priority-driven algorithm is proposed for scheduling periodic task systems upon multiprocessor platforms: this algorithm is shown to successfully schedule some task systems for which EDF may fail to meet all deadlines.

In uniform multiprocessor platforms, the various proces-sors comprising the multiprocessor platfo... more In uniform multiprocessor platforms, the various proces-sors comprising the multiprocessor platform may have dif-ferent computing capacities. The focus of this paper is the design of efficient tests for determining whether the Earliest Deadline First Scheduling Algorithm (EDF) can ...

Real-time multiprocessor systems are now commonplace. Designs range from single-chip architecture... more Real-time multiprocessor systems are now commonplace. Designs range from single-chip architectures, with a modest number of processors, to large-scale signal-processing systems, such as synthetic-aperture radar systems. For uniprocessor systems, the problem of ensuring that deadline constraints are met has been widely studied: effective scheduling algorithms that take into account the many complexities that arise in real systems (e.g., synchronization costs, system overheads, etc.) are well understood. In contrast, researchers are just beginning to understand the trade-offs that exist in multiprocessor systems. In this chapter, we analyze the trade-offs involved in scheduling independent, periodic real-time tasks on a multiprocessor.

Real-time Systems, 2003

The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilizat... more The scheduling of systems of periodic tasks upon multiprocessor platforms is considered. Utilization-based conditions are derived for determining whether a periodic task system meets all deadlines when scheduled using the earliest deadline first scheduling algorithm (EDF) upon a given multiprocessor platform. A new priority-driven algorithm is proposed for scheduling periodic task systems upon multiprocessor platforms: this algorithm is shown to successfully schedule some task systems for which EDF may fail to meet all deadlines.

We have recently been studying the scheduling of real-time systems uponuniform and identical mult... more We have recently been studying the scheduling of real-time systems uponuniform and identical multiprocessor platforms. In particular, we have beenexploring the use of EDF-scheduling in such systems; this paper summarizessome of our recent ndings in this eld.