| 1. |
- Abdelzaher, T., et al.
(author)
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The aperiodic multiprocessor utilization bound for liquid tasks
- 2002
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In: 8th IEEE Real-Time and Embedded Technology and Applications Symposium, 2002. Proceedings. - 1545-3421. - 0769517390 ; , s. 173-184
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Conference paper (peer-reviewed)abstract
- Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalized by Abdelzaher and Lu to the aperiodic task case. In this paper we further generalize the aperiodic bound to the case of multiprocessors, and present key new insights into schedulability, analysis of aperiodic tasks. We consider a special task model, called the liquid task model, representative of high-performance servers with aperiodic workloads, such as network routers, web servers, proxies, and real-time databases. For this model, we derive the optimal multiprocessor utilization bound, defined on a utilization-like metric we call "synthetic utilization". This bound allows developing constant-time admission control tests that provide utilization-based absolute delay, tees. We show that the real utilization of admitted tasks can be close to unity even when synthetic utilization is kept below the bound. Thus, our results lead to multiprocessor systems which combine constant-time admission control with high utilization while making no periodicity assumptions regarding the task arrival pattern.
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| 2. |
- Andersson, Björn, 1974, et al.
(author)
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Global Priority-Driven Aperiodic Scheduling on Multiprocessors
- 2003
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In: Proceedings. International Parallel and Distributed Processing Symposium, 2003. - 1530-2075. - 0769519261
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Conference paper (peer-reviewed)abstract
- This paper studies multiprocessor scheduling for aperiodic tasks where future arrivals are unknown. A previously proposed priority-driven scheduling algorithm for periodic tasks with migration capability is extended to aperiodic scheduling and is shown to have a capacity bound of 0.5. This bound is close to the best achievable for a priority-driven scheduling algorithm. With an infinite number of processors, no priority-driven scheduling algorithm can perform better. We also propose a simple admission controller which guarantees that admitted tasks meet their deadlines and for many workloads, it admits tasks so that the utilization can be kept above the capacity bound.
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