Browsing by Author "Chen, Ya-Shu"

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A real-time configurable synchronization protocol for self-suspending process sets
(2009-08-01)
Chen, Ya-Shu
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Chang, Li-Pin
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資訊工程學系
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Department of Computer Science
While several of researchers have proposed excellent protocols on resource synchronization, little work has been done for processes that might suspend themselves for I/O access, especially when they tend to be more tolerant to multiple priority inversions. This paper presents research results extended from the concept of priority ceilings with the objective of satisfying different priority-inversion requirements for different processes. We aim at practical considerations in which processes might voluntarily give up CPU and be willing to receive more blocking time than those in more traditional approaches. Extensions on the proposed scheduling protocols for deadlock prevention are also considered.
An anomaly prevention approach for real-time task scheduling
(2009-01-01)
Chen, Ya-Shu
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Chang, Li-Pin
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Kuo, Tei-Wei
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Mok, Aloysius K.
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資訊工程學系
This research responds to practical requirements in the porting of embedded software over platforms and the well-known multiprocessor anomaly. In particular, we consider the task scheduling problem when the system configuration changes. With mutual-exclusive resource accessing, we show that new violations of the timing constraints of tasks might occur even when a more powerful processor or device is adopted. The concept of scheduler stability and rules are then proposed to prevent scheduling anomaly from occurring in task executions that might be involved with task synchronization or I/O access. Finally, we explore policies for bounding the duration of scheduling anomalies. (c) 2008 Elsevier Inc. All rights reserved.
Event-driven dynamic workload scaling for uniprocessor real-time embedded systems
(2007-09-01)
Chang, Li-Pin
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Chen, Ya-Shu
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資訊工程學系
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Department of Computer Science
Many embedded systems are designed to take timely reactions to the occurrences of particular scenarios. Such systems could sometimes experience transient overloads because of workload bursts or hardware malfunctions. Thus a mechanism to focus limited resources on the processing of urgent events is a key to retain system validity under stressing workloads. In this paper, we propose a new approach for workload Scaling in uniprocessor real-time embedded systems. The idea is to view the system as a black box, and workload scaling for overload management can be done via very intuitive primitives, i.e., how hardware events are selectively fed into the system. Such a new approach removes the need for the adjustments of task periods and task phasing, which is important for many workload-scaling techniques. The proposed approach is implemented in a real-time surveillance system. Experimental results show that the system still delivers good accuracy and high responsiveness for visual-object tracking under the presence of overloads.
Multiprocessor Frequency Locking for Real-Time Task Synchronization
(2008-01-01)
Chen, Ya-Shu
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Chang, Li-Pin
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Kuo, Tei-Wei
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資訊工程學系
;
Department of Computer Science
Energy-efficient real-time task scheduling is complicated by the deployment of co-processors. The problem complexity comes from the complexity in multiprocessor task scheduling and the difficulty in the trading of priority inversion with energy consumption. In this paper, a multiprocessor task synchronization protocol is proposed by locking the frequency of each (co-)processor and synchronizing resource sharing of tasks in a systematic way and with cross-(co)processor considerations. The well-known Priority Ceiling Protocol is taken as an example for its extension on energy-efficient real-time multiprocessor scheduling. The objective is to minimize the energy consumption of a task set and, at the same time, meet the task deadlines. The capability of the proposed methodology is evaluated by a series of experiments, for which encouraging results are presented.
On-Line Task Scheduling for Dual-Core Real-Time Embedded Systems
(2009)
Chen, Ya-Shu
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Chang, Li-Pin
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Cheng, Chia-Ming
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資訊工程學系
;
Department of Computer Science
On-line task scheduling is a very challenging issue for dual-core real-time embedded systems, because to control priority inversion and to manage system utilization are fundamentally at odds with each other. We propose an on-line dual-core scheduling framework for dynamic workloads with real-time constraints. The processor and the co-processor axe dedicated to separate schedulers with different scheduling policies, and precedence constraints among tasks are dealt with the interaction between the two schedulers. We have shown that our proposed scheduling can achieve a good balance between high system utilization and stable task response under realistic workloads.