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M/G/1 Preemptive Priority Queues With Finite and Infinite Buffers (유한 및 무한 용량 대기열을 가지는 선점 우선순위 M/G/1 대기행렬)

  • Kim, Kilhwan
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.43 no.4
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    • pp.1-14
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    • 2020
  • Recently, M/G/1 priority queues with a finite buffer for high-priority customers and an infinite buffer for low-priority customers have applied to the analysis of communication systems with two heterogeneous traffics : delay-sensitive traffic and loss-sensitive traffic. However, these studies are limited to M/G/1 priority queues with finite and infinite buffers under a work-conserving priority discipline such as the nonpreemptive or preemptive resume priority discipline. In many situations, if a service is preempted, then the preempted service should be completely repeated when the server is available for it. This study extends the previous studies to M/G/1 priority queues with finite and infinite buffers under the preemptive repeat-different and preemptive repeat-identical priority disciplines. We derive the loss probability of high-priority customers and the waiting time distributions of high- and low-priority customers. In order to do this, we utilize the delay cycle analysis of finite-buffer M/G/1/K queues, which has been recently developed for the analysis of M/G/1 priority queues with finite and infinite buffers, and combine it with the analysis of the service time structure of a low-priority customer for the preemptive-repeat and preemptive-identical priority disciplines. We also present numerical examples to explore the impact of the size of the finite buffer and the arrival rates and service distributions of both classes on the system performance for various preemptive priority disciplines.

A Model for Reducing Priority Inversion in Real Time Server System (실시간 서버 시스템에서 우선 순위 반전현상을 감소하기 위한 모델)

  • Choe, Dae-Su;Im, Jong-Gyu;Gu, Yong-Wan
    • The Transactions of the Korea Information Processing Society
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    • v.6 no.11
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    • pp.3131-3139
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    • 1999
  • Satisfying the rigid timing requirements of various real-time activities in real-time systems often requires some special methods to tune the systems run-time behaviors. Unbounded blocking can be caused when a high priority activity cannot preempt a low priority activity. In such situation, it is said that a priority inversion has occurred. The priority inversion is one of the problems which may prevent threads from meeting the deadlines in the real-time systems. It is difficult to remove such priority inversion problems in the kernel at the same time to bound the worst case blocking time for the threads. A thread is a piece of executable code which has access to data and stack. In this paper, a new real-time systems. It is difficult to remove such priority inversion problems in the kernel at the same time to bound the worst case blocking time for the threads. A threads is a piece of executable code which has access to data and stack. In this paper, a new real-time server model, which minimizes the duration of priority inversion, is proposed to reduce the priority inversion problem. The proposed server model provides a framework for building a better server structure, which can not only minimize the duration of the priority inversion, but also reduce the deadline miss ratio of higher priority threads.

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Priority Setting of New Promising IT Industries (IT 유망 신산업의 우선순위 평가)

  • Lee, Jang-U;Min, Wan-Gi
    • Journal of Technology Innovation
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    • v.13 no.1
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    • pp.25-54
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    • 2005
  • In this study, priority setting model of new promising IT industries which will be the growth engines for the Korean IT industry, was established. Based on the AHP model, priority setting of IT new promising IT industries was conducted. Firstly, the selection cases of the new promising IT industries and major priority setting methodologies including the AHP methodology, were analyzed. The AHP model was selected as the most feasible methodology for priority setting of the new IT industries, among the various priority setting methodologies. Secondly, in setting up the AHP model for prioritization of the new promising If industries, a 'goal' was established to be priority setting of the new promising IT industries, and an 'alternatives' to be 18 new promising IT industries. Then a logical and a systematic assessment criteria including 5 main criteria('Technological Innovation', 'Market Ability', 'SPin-off Effect', 'Public Benefit', 'Strategic Importance') and 14 sub-criteria, were developed for priority setting of the 18 new promising industries. Finally, with the AHP model, the substantial analysis was made to set up priority of the 18 new promising IT industries. The substantial analysis showed the following priority setting results and implications for the 18 new promising IT industries.

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(N, n)-Preemptive Repeat-Different Priority Queues ((N, n)-선점 재샘플링-반복 우선순위 대기행렬)

  • Kim, Kilhwan
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.40 no.3
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    • pp.66-75
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    • 2017
  • Priority disciplines are an important scheme for service systems to differentiate their services for different classes of customers. (N, n)-preemptive priority disciplines enable system engineers to fine-tune the performances of different classes of customers arriving to the system. Due to this virtue of controllability, (N, n)-preemptive priority queueing models can be applied to various types of systems in which the service performances of different classes of customers need to be adjusted for a complex objective. In this paper, we extend the existing (N, n)-preemptive resume and (N, n)-preemptive repeat-identical priority queueing models to the (N, n)-preemptive repeat-different priority queueing model. We derive the queue-length distributions in the M/G/1 queueing model with two classes of customers, under the (N, n)-preemptive repeat-different priority discipline. In order to derive the queue-length distributions, we employ an analysis of the effective service time of a low-priority customer, a delay cycle analysis, and a joint transformation method. We then derive the first and second moments of the queue lengths of high- and low-priority customers. We also present a numerical example for the first and second moments of the queue length of high- and low-priority customers. Through doing this, we show that, under the (N, n)-preemptive repeat-different priority discipline, the first and second moments of customers with high priority are bounded by some upper bounds, regardless of the service characteristics of customers with low priority. This property may help system engineers design such service systems that guarantee the mean and variance of delay for primary users under a certain bounds, when preempted services have to be restarted with another service time resampled from the same service time distribution.

Study on the Priority Decision for Redevelopment of Agricultural Reservoir (농업용저수지 재개발 우선순위 결정 연구)

  • Kim, Hae-Do;Kim, Sun-Joo;Lee, Kwang-Ya
    • Journal of The Korean Society of Agricultural Engineers
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    • v.51 no.6
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    • pp.63-68
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    • 2009
  • Most of agricultural reservoirs in Korea have no function of flood control except 5% of reservoirs even exposed to natural disaster. In addition, there are increasing needs for the reservoir to guarantee the release of environmental flow to the downstream. Thus, the purpose of this paper is to study the priority decision method for the reservoir redevelopment satisfying both water utilization and flood control. The major scopes of this research are to set up six priority indices and to make needed GIS data for calculating each priority. There is important consideration of obtaining the data or not in deciding the indices. Although the detailed indices is expected to better reflect redevelopment priority but the subjective indices like, 'opinion' and 'landscape' are excluded. From the results, it will enables the six priority indices to really assist in decision redevelopment priority of agricultural reservoirs.

Priority-based Overlay Multicast for Distributed Interactive Application (Distributed Interactive Application을 위한 우선 순위 기반 오버레이 멀티캐스트)

  • Lee, Hyung-Ok;Nam, Ji-Seung
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.1367-1369
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    • 2013
  • Applying Application-Level Multicast technology (ALM) to Distributed Interactive Applications (DIAs) becomes more and more popular. Especially for DIAs embedded priority that the sender forwards data to receivers due to their respective priorities. The priority-based directed minimum spanning tree (PST) algorithm was designed for these DIAs. However, the PST has no efficient priority selection and filtering mechanism. The system will consume a tremendous amount of resource for reconstructing distribution tree and becomes unstable and unscalable. In this paper, First, We propose a novel priority-based application level multicast algorithm: Predict-and-Quantize for Priority with directed minimum Spanning Tree (PQPST), which can efficiently predict efficient priorities for the receivers and quantize the predicted priorities to build the multicast distribution tree. Second, we propose Priority Discrepancy Heuristic Mechanism (PDHM), which sets different thresholds of priority discrepancy within the priority discrepancy interval to control the distribution tree construction can efficiently decrease the repeated distribution tree construction, and we get the best heuristic priority discrepancy interval by PQPST. According to the simulation results, the PQPST and PDHM can efficiently improve the performance of the PST algorithm.

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Total Resource Requirements-Based Priority Queuing Scheme for DS/CDMA Cellular Networks

  • Piao, Shiquan;Park, Jae-Won;Park, Yong-Wan
    • ETRI Journal
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    • v.28 no.3
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    • pp.371-374
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    • 2006
  • We propose and analyze a priority queuing scheme that gives priority in the same class of calls according to their total resource requirements (TRRs). The proposed scheme gives a higher priority to the calls that have a lower TRR over the calls that have a higher TRR. The numerical results show that the proposed priority queuing scheme provides better performance than the traditional queuing schemes in call blocking probability.

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A Priority Scheme for IEEE 802.11 Wireless LAN

  • Jang, Yeong-Min
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.12B
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    • pp.1996-2002
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    • 2000
  • This paper investigates a priority scheme for IEEE 802.11 Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol in order to provide short access times for priority frames (e.g. time-deadline traffic) even when the overall traffic on the wireless channel is heavy. Under the compatibility constraint for the IEEE 802.11 wireless LANs, two priority systems are simulated: no priority (current IEEE 802.11 standard) for time-deadline traffics and dynamic time-deadline priority. We evaluate algorithms to improve the time-deadline traffic performance using discrete event simulation (DES)

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A Study on the Queueing with Dynamic Priority in Communication Network (통신망에서의 동적우선도큐잉에 관한 연구)

  • 이재호;송영재
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.12 no.2
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    • pp.92-101
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    • 1987
  • Messages which are entered into communication networks are processed according to the priorities manipulated by serveral queueing disciplines. This study is concerned with one of those disciplines, dynamic priority. We analyzed the everage waiting time for the messages be processed by dynamic priority in queue. The priority is variated by the message's waiting time in queue. The dynamic priority discipline can be classified according as messaged have initial priority or not. Difference of above two discriplines were considered.

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Design and Implementation of a Protocol for Solving Priority Inversion Problems in Real-time OS (실시간 운영체제의 우선순위 역전현상 해결을 위한 프로토콜 설계 및 구현)

  • Kang, Seong-Goo;Gyeong, Gye-Hyeon;Ko, Kwang-Sun;Eom, Young-Ik
    • The KIPS Transactions:PartA
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    • v.13A no.5
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    • pp.405-412
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    • 2006
  • Real-time operating systems have been used in various computing environments, where a job must be completed in its deadline, with various conditions, such as effective scheduling policies, the minimum of an interrupt delay, and the solutions of priority inversion problems, that should be perfectly satisfied to design and develop optimal real-time operating systems. Up to now, in order to solve priority inversion problems among several those conditions. There have been two representative protocols: basic priority inheritance protocol and priority ceiling emulation protocol. However, these protocols cannot solve complicated priority inversion problems. In this paper, we design a protocol, called recursive priority inheritance (RPI), protocol that effectively solves the complicated priority inversion problems. Our proposed protocol is also implemented in the Linux kernel and is compared with other existing protocols in the aspect of qualitative analysis.