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211
Integrating Multimedia Applications in Hard Real-Time Systems
- in Proc. 19th IEEE Real-Time Systems Symposium (RTSS’98
, 1998
"... This paper focuses on the problem of providing efficient run-time support to multimedia applications in a real-time system, where two types of tasks can coexist simultaneously: multimedia soft real-time tasks and hard real-time tasks. Hard tasks are guaranteed based on worst case execution times and ..."
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Cited by 318 (51 self)
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This paper focuses on the problem of providing efficient run-time support to multimedia applications in a real-time system, where two types of tasks can coexist simultaneously: multimedia soft real-time tasks and hard real-time tasks. Hard tasks are guaranteed based on worst case execution times and minimum interarrival times, whereas multimedia and soft tasks are served based on mean parameters. The paper describes a server-based mechanism for scheduling soft and multimedia tasks without jeopardizing the a pri-ori guarantee of hard real-time activities. The performance of the proposed method is compared with that of similar service mechanisms through extensive simulation experi-ments and several multimedia applications have been im-plemented on the HARTIK kernel. 1.
A model of hierarchical real-time virtual resources
- In Proc. of IEEE Real-Time Systems Symposium
, 2002
"... A real-time virtual resource is an abstraction for resource sharing where application task groups must meet timing constraints and knowledge of all the timing requirements may not be available for a global schedulability analysis, such as is the case in the open system environment. In [12], we intro ..."
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Cited by 107 (1 self)
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A real-time virtual resource is an abstraction for resource sharing where application task groups must meet timing constraints and knowledge of all the timing requirements may not be available for a global schedulability analysis, such as is the case in the open system environment. In [12], we introduced the notion of a real-time virtual resource which operates at a fraction of the rate of the shared physical resource and whose rate of service provision varies with time but is bounded. The shared resource is partitioned into real-time virtual resources by a resource-level scheduler such that each real-time virtual resource is accessible only by an individual application task group; tasks within the same task group are scheduled by an application-tasklevel scheduler that is specialized to the real-time requirements of the tasks in the group. In this paper, we propose a hierarchical real-time virtual resource model that permits resource partitioning to be extended to multiple levels. Through this model, partitions on each level are scheduled as if they had access to a dedicated resource and there is minimal interference between neighboring partition levels. We also investigate the partitioning of real-time virtual resources subject to scheduling quantum requirements.
Resource partitioning among real-time applications
- IN PROCEEDINGS OF EUROMICRO CONFERENCE ON REAL-TIME SYSTEMS
, 2003
"... When executing different real-time applications on a single processor system, one problem is how to compose these applications and guarantee at the same time that their timing requirements are not violated. A possible way of composing applications is through the resource reservation approach. Each a ..."
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Cited by 104 (17 self)
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When executing different real-time applications on a single processor system, one problem is how to compose these applications and guarantee at the same time that their timing requirements are not violated. A possible way of composing applications is through the resource reservation approach. Each application is handled by a dedicated server that is assigned a fraction of the processor. Using this approach, the system can be seen as a two-level hierarchical scheduler. A considerable amount of work has been recently addressed to the analysis of this kind of hierarchical systems. However, a question is still unanswered: given a set of real-time tasks to be handled by a server, how to assign the server parameters so that the task set is feasible? In this paper, we answer to the previous question for the case of fixed priority local scheduler by presenting a methodology for computing the class of server parameters that make the task set feasible.
Hierarchical fixed priority pre-emptive scheduling
- In Proceedings of the 26 th IEEE International Real-Time Systems Symposium (RTSS’05
, 2005
"... This report focuses on the hierarchical scheduling of systems where a number of separate applications reside on a single processor. It addresses the particular case where fixed priority pre-emptive scheduling is used at both global and local levels, with periodic or deferrable servers associated wit ..."
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Cited by 93 (6 self)
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This report focuses on the hierarchical scheduling of systems where a number of separate applications reside on a single processor. It addresses the particular case where fixed priority pre-emptive scheduling is used at both global and local levels, with periodic or deferrable servers associated with each application. Using response time analysis, an exact schedulability test is derived for application tasks. This test improves on previously published work. The analysis is extended to the specific case of harmonic tasks that can be bound to the release of their server. These tasks exhibit improved schedulability indicating that it is advantageous to choose server periods that enable some tasks to be bound to the release of their server. The use of Periodic, Sporadic and Deferrable Servers is considered with the conclusion that the simple Periodic Server dominates both Sporadic and Deferrable Servers when the metric is application task schedulability. As an adjunct some interesting results are presented on the optimal priority ordering of a set of Deferrable Servers, rate-monotonic priority ordering is not optimal in this case. The second part of the report investigates the problem of selecting the optimal set of server parameters. Analysis of this problem reveals a simple method for determining the optimal set of server capacities given fixed server periods and priorities. Despite this advance, empirical results show that server parameter selection exhibits dependencies between the set of servers and so the locally optimum selection of parameters for one server often does not result in an overall selection of parameters that is either schedulable or results in the maximum remaining system utilisation. The selection of server parameters is a holistic problem that may in practice only be soluble via search; a greedy approach to parameter selection is demonstrated to be ineffective.
Compositional analysis framework using EDP resource models
- IN PROCEEDINGS OF THE 28 TH IEEE INTERNATIONAL REAL-TIME SYSTEMS SYMPOSIUM
, 2007
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Capacity Sharing for Overrun Control
- IEEE Real-Time Systems Symposium
, 2000
"... In this paper, we present a general scheduling methodology for managing overruns in a real-time environment, where tasks may have different criticality and flexible timing constraints. The proposed method achieves isolation among tasks through a resource reservation mechanism which bounds the effect ..."
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Cited by 65 (8 self)
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In this paper, we present a general scheduling methodology for managing overruns in a real-time environment, where tasks may have different criticality and flexible timing constraints. The proposed method achieves isolation among tasks through a resource reservation mechanism which bounds the effects of task interference, but also performs efficient reclaiming of the unused computation times to relax the utilization constraints imposed by isolation. The enhancements achieved by the proposed approach resulted to be very effective with respect to classical reservation schemes. The performance has been evaluated by implementing the algorithm on a real-time kernel. The runtime overhead introduced by the scheduling mechanism has also been investigated with specific experiments, in order to be taken into account in the schedulability analysis. However, it resulted to be negligible in most practical cases.
Resource reservation in dynamic real-time systems
- Real-Time Systems
, 2004
"... Abstract. This paper focuses on the problem of providing ef®cient run-time support to multimedia applications in a real-time system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical real-time tasks (hard tasks) are guaranteed based on worst-case ex ..."
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Cited by 62 (13 self)
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Abstract. This paper focuses on the problem of providing ef®cient run-time support to multimedia applications in a real-time system, where different types of tasks (characterized by different criticality) can coexist.Whereas critical real-time tasks (hard tasks) are guaranteed based on worst-case execution times and minimum interarrival times, multimedia tasks are served based on mean parameters.A novel bandwidth reservation mechanism (the constant bandwidth server) allows real-time tasks to execute in a dynamic environment under a temporal protection mechanism, so that each task will never exceed a prede®ned bandwidth, independently of its actual requests.The paper also discusses how the proposed server can be used for handling aperiodic tasks ef®ciently and how a statistical analysis can be applied to perform a probabilistic guarantee of soft tasks.The performance of the proposed method is compared with that of similar service mechanisms (dynamic real-time servers and proportional share schedulers) through extensive simulation experiments.
Hierarchical scheduling framework for virtual clustering of multiprocessors
, 2008
"... Scheduling of sporadic task systems on multiprocessor platforms is an area which has received much attention in the recent past. It is widely believed that finding an optimal scheduler is hard, and therefore most studies have focused on developing algorithms with good utilization bounds. These algor ..."
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Cited by 62 (5 self)
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Scheduling of sporadic task systems on multiprocessor platforms is an area which has received much attention in the recent past. It is widely believed that finding an optimal scheduler is hard, and therefore most studies have focused on developing algorithms with good utilization bounds. These algorithms can be broadly classified into two categories: partitioned scheduling in which tasks are statically assigned to individual processors, and global scheduling in which each task is allowed to execute on any processor in the platform. In this paper we consider a third, more general, approach called cluster-based scheduling. In this approach each task is statically assigned to a processor cluster, tasks in each cluster are globally scheduled among themselves, and clusters in turn are scheduled on the multiprocessor platform. We develop techniques to support such cluster-based scheduling algorithms, and also consider properties that minimize processor utilization of individual clusters. Since neither partitioned nor global strategies dominate over the other, cluster-based scheduling is a natural direction for research towards achieving improved utilization bounds. 1
