• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1631-1639
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• 2010

This paper proposes a scheduling algorithm that can reduce the power consumed for execution of application programs and the communication cost incurred due to dependencies among tasks. The proposed scheduling algorithm can increase energy efficiency of the DVS(Dynamic Voltage Scaling) by estimating laxity usage during scheduling, making up for conventional algorithms that apply the DVS after scheduling. Energy efficiency can be increased by applying the proposed algorithm to complex multimedia applications. Experimental results show that energy consumptions for executing HD MPEG4, MotionJPEG codec, MP3, and Wavelet have been reduced by 11.2% on the average, when compared to conventional algorithms.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.3
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• pp.234-240
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• 1999

This paper presents a new approach for large-scale generator maintenance scheduling optimizations. The generator preventive maintenance scheduling problems are typical discrete dynamic n-dimensional vector optimization ones with several inequality constraints. The considered objective function to be minimized a subset of{{{{ { R}^{n } }}}} space is the variance (i.g., second-order momentum) of operating reserve margin to levelize risk or reliability during a year. By its nature of the objective function, the optimal solution can only be obtained by enumerating all combinatorial states of each variable, a task which leads to computational explosion in real-world maintenance scheduling problems. This paper proposes a new priority search mechanism based on each generator's discrete sensitivity value which was analytically developed in this study. Unlike the conventional capacity-based priority search, it can prevent the local optimal trap to some extents since it changes dynamically the search tree in each iteration. The proposed method have been applied to two test systems (i.g., one is a sample system with 10 generators and the other is a real-world lage scale power system with 280 generators), and the results anre compared with those of the conventional capacith-based search method and combinatorial optimization method to show the efficiency and effectiveness of the algorithm.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.11-16
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• 2010

This paper compares and studies scheduling methods to reduce jitter in real-time control systems. While previous research has focused on dynamic-priority scheduling schemes, this paper focuses on fixed-priority scheduling which is more widely used. It is pointed out that previously defined jitter measures might not be useful in enhancing the control performance of a real-time task because the measures are relative values. We present a new jitter measure and a new scheduling scheme for fixed-priority tasks. The experimental results through simulation show that the new scheduling scheme reduces jitter and enhances control performance.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.6
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• pp.273-283
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• 2008

Many embedded real-time systems have adopted processors supported with dynamic voltage scaling(DVS) recently. Power is one of the important metrics for optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor supported with DVS. In this paper, we propose heuristic algorithms to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. The previous algorithm has a following constraint : given the tasks are ordered in a nondecreasing order of their relative deadline, the task slowdown factors computed are in a nonincreasing order. In this paper, we relax the constraint and propose heuristic algorithms which have the same time complexity that previous algorithm has and can save more energy. Experimental results show that the proposed algorithms are energy efficient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.866-874
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• 2006

This paper proposes a new Dynamic Voltage Scaling(DVS) algorithm to achieve low-power scheduling of aperiodic hard real-time tasks. Aperiodic tasks schedulingcannot be applied to the conventional DVS algorithm and result in consuming energy more than periodic tasks because they have no period, non predictable worst case execution time, and release time. In this paper, we defined Virtual Periodic Task Set(VTS) which has constant period and worst case execution time, and released aperiodic tasks are assigned to this VTS. The period and worst case execution time of the virtual task can be obtained by calculating task utilization rate of both periodic and aperiodic tasks. The proposed DVS algorithm scales the frequency of both periodic and aperiodic tasks in VTS. Simulation results show that the energy consumption of the proposed algorithm is reduced by 11% over the conventional DVS algorithm for only periodic task.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.245-252
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• 2001

Multicomputer systems achieve high performance by utilizing a number of computing nodes. Multidimensional meshes have become popular as multicomputer architectures due to their simplicity and efficiency. In this paper we propose an efficient processor allocation scheme for 3D torus based on first-fit approach. The scheme minimizes the allocation time by effectively manipulating the 3D information an 2D information using CST (Coverage Status Table). Comprehensive computer simulation reveals that the allocation time of the proposed scheme is always smaller than the earlier scheme based on best-fit approach, while allowing comparable processor utilization. The difference gets more significant as the input load increases. To investigate the performance of the proposed scheme with different scheduling environment, non-FCFs scheduling policy along with the typical FCFS policy is also studied.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.158-163
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• 1986

This article surveys techniques and issues related to real time process control system developed for industrial control applications. It covers the system architecture and software engineering issues such as the design of data structures, scheduling of asynchronous task activities, management of shared resources, handling of interrupt and implementing an user friendly man-machine interface. Also problems associated with implementing a real-time system that supports dynamic configuration of data base is addressed.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.565-567
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• 2004

배터리를 효율적으로 사용하기 위한 기존 연구에서 제한된 용량의 배터리를 최대한 연장하여 사용하는 방법들에 관하여 다루었다. 본 논문에서는 시스템을 사용하는 정해진 시간동안 배터리가 소진되지 않도록, 시스템에서 동작하는 작업량을 동적으로 조절하는 방법을 제시한다. 제시된 방법에서는 시스템에서 동작하는 작업들을 중요성에 따라 분류하고, 시스템을 연동시키는 배터리 잔량을 주기적으로 측정한다. 그리고 측정된 배터리 잔량이 충분하면 모든 작업들을 동작시키고 배터리 잔량이 부족하면 중요성이 떨어지는 작업들부터 동작을 정지시켜서 전체 작업량을 감소시키고, 이를 통하여 배터리 지속 시간을 점진적으로 연장시키는 방법이다

• The KIPS Transactions:PartA
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• v.14A no.6
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• pp.357-362
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• 2007

In distributed systems like cluster systems, in order to get more performance improvement, the initial task placement system precisely estimates and correctly assigns the resource requirement by the process. The resource-based initial job placement scheme needs the prediction of resource usage of a task in order to fit it to the most suitable hosts. However, the wrong prediction of resource usage causes serious performance degradation in dynamic load balancing systems. Therefore, in this paper, to resolve the problem due to the wrong prediction, we propose a new load metric. By the new load metric, the resource-based initial job placement scheme can work without priori knowledge about the type of process. Simulation results show that the dynamic load balancing system using the proposed approach achieves shorter execution times than the conventional approaches.

• KIISE Transactions on Computing Practices
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• v.24 no.1
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• pp.10-16
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• 2018

The task of consolidating server workloads is critical for the efficiency of a datacenter in terms of reducing costs. However, as a greater number of workloads are consolidated in a single server, the performance of workloads might be degraded due to their contention to the limited shared resources. To reduce the performance degradation, scheduling for mitigating the contention of shared resources is necessary. In this paper, we present the Dynamic Voltage Frequency Scaling (DVFS) based memory-contention aware scheduling method for multi-threaded workloads. The proposed method uses two approaches: running memory-intensive threads on the limited cores to avoid concurrent memory accesses, and reducing the frequencies of the cores that run memory-intensive threads. With the proposed algorithm, we increased performance by 43% and reduced power consumption by 38% compared to the Completely Fair Scheduler(CFS), the default scheduler of Linux.