• Journal of KIISE:Computer Systems and Theory
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• v.29 no.11
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• pp.611-621
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• 2002

For real-time systems, multiprocessor support is indispensable to handle the large number of requests. Existing real-time on-line scheduling algorithms such as Earliest Deadline First Algorithm (EDF) and Least Laxity Algorithm (LLA) may not be suitable for scheduling real-time tasks in multiprocessor systems. Although EDF has low context switching overhead, it suffers from "multiple processor anomalies." LLA has been shown as suboptimal, but has the potential for higher context switching overhead. Earliest Deadline Zero Laxity (EDZL) solved somewhat the problems of those algorithms, however is suboptimal for only two processors. Another algorithm EDA2 shows very good performance in overload phase, however, is not suboptimal for muitiprocessors. We propose two on-line scheduling algorithms, Earliest Deadline/Least Laxity (ED/LL) and ED2/LL. ED/LL is suboptimal for multiprocessors, and has low context switching overhead and low deadline miss rate in normal load phase. However, ED/LL is ineffective when the system is overloaded. To solve this problem, ED2/LL uses ED/LL or EDZL in normal load phase and uses EDA2 in overload phase. Experimental results show that ED2/LL achieves good performance in overload phase as wet] as in normal load phase.oad phase.

• Journal of the Korea Society for Simulation
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• v.22 no.1
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• pp.77-86
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• 2013

Cloud computing is one of the distributed computing environments and utilizes several computing resources. Cloud environment uses a virtual machine to process a requested job. To balance a workload and process a job rapidly, cloud environment uses a provisioning technique and assigns a task with a status of virtual machine. However, a scheduling method for cloud computing requires a definition of virtual machine availabilities, which have an obscure meaning. In this paper, we propose Fuzzy logic driven Virtual machine Provisioning scheduling using Resource Evaluation(FVPRE). FVPRE analyzes a state of every virtual machine and actualizes a value of resource availability. Thus FVPRE provides an efficient provisioning scheduling with a precise evaluation of resource availability. FVPRE shows a high throughput and utilization for job processing on cloud environments.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.5
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• pp.111-118
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• 2019

Recent graphic processing units (GPUs) provide high throughput by using powerful hardware resources. However, massive memory accesses cause GPU performance degradation due to cache inefficiency. Therefore, the performance of GPU can be improved by reducing thread parallelism when cache suffers memory contention. In this paper, we propose a dynamic warp scheduler which controls thread parallelism according to degree of cache contention. Usually, the greedy then oldest (GTO) policy for issuing warp shows lower parallelism than loose round robin (LRR) policy. Therefore, the proposed warp scheduler employs the LRR warp scheduling policy when Miss Status Holding Register(MSHR) utilization is low. On the other hand, the GTO policy is employed in order to reduce thread parallelism when MSHRs utilization is high. Our proposed technique shows better performance compared with LRR and GTO policy since it selects efficient scheduling policy dynamically. According to our experimental results, our proposed technique provides IPC improvement by 12.8% and 3.5% over LRR and GTO on average, respectively.

• Journal of the Korea Computer Industry Society
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• v.8 no.3
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• pp.197-206
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• 2007

The waiting delays of internet VOD users are inevitable in this policy since the services are not taken immediately upon requests but upon every scheduling points. An inefficient management of such delays makes an unfair service to users and increases the possibility of higher reneging rates. This paper proposes an efficient service scheduling scheme which improves the average waiting time of users requests and reduces the starvation problem of users requesting less popular movies. Experimental results of simulations show that the proposed scheme improves about 20 percentage of average waiting time and reduces significantly the starving requesters comparing with those of conventional methods such as FCFS and MQL.

• Journal of the Korea Society for Simulation
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• v.21 no.2
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• pp.59-67
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• 2012

A grid computing consists of the physical resources for processing one of the large-scale jobs. However, due to the recent trends of rapid growing data, the grid computing needs a parallel processing method to process the job. In general, each physical resource divides a requested large-scale task. And a processing time of the task varies with an efficiency and a distance of each resource. Even if some resource completes a job, the resource is standing by until every divided job is finished. When every resource finishes a processing, each resource starts a next job. Therefore, this paper proposes a dynamic resource reallocation scheduling model (DDRSM). DDRSM finds a waiting resource and reallocates an unfinished job with an efficiency and a distance of the resource. DDRSM is an efficient method for processing multiple large-scale jobs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.733-735
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• 2012

Real-Time Aperiodic Tasks Scheduling Using Synthetic Utilization on Multiprocessor Systems has a drawback in that if some tasks, even though they are completed and have no more execution times, are included in the current invocation set, their execution times and deadlines are added to the synthetic utilization. This may lead to a problem in which actually schedulable tasks are decided not to be schedulable. In this paper, we recognize the above mentioned problem and propose an improved synthetic utilization method that can be used to schedule aperiodic tasks more efficiently on multiprocessor systems.

• The KIPS Transactions:PartB
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• v.11B no.7 s.96
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• pp.803-812
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• 2004

The performance of video-on-demand(VOD) systems is known to be mainly dependent on a scheduling mechanism which they employ. Broadcast-based scheduling schemes have attracted a lot of attention as an efficient way of distributing popular videos to very large client populations. The main motivations of broadcasting scheduling mechanisms are that they scale up extremely well and they have very modest bandwidth requirements. This paper studies this issue and proposes a new broadcasting scheduling mechanism, named fast universal video dis-tribution(FUVD). FUVD scheme dynamically constructs a video broadcasting schedule in response to client requests, and broadcasts video seg-ments according to this schedule. This paper also evaluates the performance of FUVD on the basis of a simulation approach. The simulation results indicate that FUVD protocol shows a superior performance over UD, CBHD, and NPB in terms of the average response time.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.368-369
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• 2011

현대의 스토리지 디바이스들은 디바이스 내부에 캐시를 가지고 있다. 스토리지 디바이스 내부의 캐시에서 입출력 요청이 전송 될 경우 운영체제는 문맥 전환을 하지 않아도 될 것이다. 본 연구에서는 입출력 스케줄러의 효율적인 스케줄링을 위한 정보를 제공하기 위해 캐시 적중 예측 기법을 제시하였다. 또한 실제 스토리지 디바이스를 대상으로 한 실험을 통해 실제 스토리지 디바이스의 캐시 패턴과 캐시 적중 시와 캐시 미스 시의 응답시간의 상이성을 살펴보고 캐시 적중 예측 기법을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1099-1102
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• 2000

입출력버퍼형 스위치를 위한 간단한 셀 스케줄링 알고리즘을 제시한다. 스위치는 고속동작 및 성능 향상을 위해 이중 스위칭 플랜을 갖고 있다. 제안한 알고리즘은 각각의 스위칭 플랜에서 독립적으로 수행되며 전송요청 (request), 전송허가(grant). 전송확정 (accept)의 3 단계 동작으로 이루어져 있다. 또한 각 3 단계동작을 한 셀시간에 한 번씩만 수행하여 단위 셀시간이 작은 고속 스위칭에 적합하다. 모의실험 결과 제안한 알고리즘의 성능이 Bernoulli 트래픽 입력에 대해 출력버퍼형 스위치의 성능과 거의 동일하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.46-48
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• 2005

본 논문에서는 병렬 컴퓨팅의 스케줄링 시스템인 EASY Backfilling 알고리즘에 기반한 작업 패킹 기법의 최적화에 대해 논의한다. 이를 위해 최적의 작업 집합을 구성하기 위한 탐색 기법으로 유전자 알고리즘을 활용하여 작업 패킹을 효율적으로 수행함과 동시에, 적은 노드를 요청한 작업에 가중치를 부여함으로써 다수 작업의 동시 실행을 우선 고려하게 하였다. 스케줄링 정책은 컴퓨터 성능에 직접적인 영향을 미치는 요소이기 때문에 시스템 부하별로 각 워크로드의 평균 대기 시간을 측정한 실험을 통해 제안 기법이 전반적인 병렬 컴퓨팅의 성능을 개선함을 확인하였다.