• Journal of KIISE:Computer Systems and Theory
• /
• v.29 no.7
• /
• pp.369-376
• /
• 2002

Although LRU is not adequate for database that has non-uniform reference pattern, it has been adopted in most database systems due to the absence of the proper alternative. We analyze database block reference pattern with the realistic database trace. Based on this analysis, we propose a new cache replacement policy. Trace analysis shows that extremely non-popular blocks take up about 70 % of the entire blocks. The influence of recency on blocks' re-reference likelihood is at first strong due to temporal locality, however, it rapidly decreases and eventually becomes negligible as stack distance increases. Based on this observation, RCB(Reference Characteristic Based) cache replacement policy, which we propose in this paper, classifies the entire blocks into four block groups by blocks' recency and re-reference likelihood, and operates different priority evaluation methods for each block group. RCB policy evicts non-popular blocks more quickly than the others and evaluates the priority of the block by frequency that has not been referenced for a long time. In a trace-driven simulation, RCB delivers a better performance than the existing polices(LRU, 2Q, LRU-K, LRFU). Especially compared to LRU. It reduces miss count by 5~l2.7%. Time complexity of RCB is O(1), which is the same with LRU and 2Q and superior to LRU-K(O(log$_2$N)) and LRFU(O(l) ~ O(log$_2$N)).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.7A
• /
• pp.1170-1181
• /
• 2001

본 논문은 다양한 실시간 스케줄링 알고리즘과 자원 접근 제어 정책을 통합적으로 설계/구현하되 필요에 따라 시스템을 선택적으로 재구성할 수 있게 하는 통합 실시간 스케줄링 모델을 제안한다. 제안 모델은 [3, 4]에서 제안된 기존 모델에 자원 관리자 및 대기 큐 관리자가 추가되었다. 사용자는 태스크 및 자원 속성을 기반 스케줄링 알고리즘에 상관없이 동일하게 지정할 수 있다. 반면 시스템 설계자는 우선순위 역전 문제를 해결하고 공유 자원에 대한 한정된 블록킹 시간을 보장하기 위한 다양한 자원 접근 제어 정책들을 하위 단계의 복잡한 커널 모듈을 수정하지 않고도 효율적으로 개발할 수 있다. Real-Time Linux [6]에 제안된 스케줄러 모델을 구현한 후, 이를 기반으로 다양한 스케줄링 알고리즘과 자원 접근 제어 정책들을 시험적으로 구현하여 보았다. 여러 성능 실험을 통해 제안 모델을 기반으로 다양한 알고리즘과 정책을 구현한다 해도 실행시의 오버헤드는 크지 않은 반면, 시스템 재구성과 자원 접근 제어 정책을 효과적으로 지원할 수 있다는 것을 확인할 수 있었다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.33 no.6
• /
• pp.337-343
• /
• 2006

The Stack Resource Policy (SRP) is a real-time synchronization protocol with some distinct properties. One of such properties is early blocking; the execution of a job is delayed instead of being blocked when requesting shared resources. If SRP is used with dynamic priority scheduling such as Earliest Deadline First (EDF), the early blocking requires that a scheduler should select the highest-priority job among the jobs that will not be blocked, incurring runtime overhead. In this paper, we analyze the runtime overhead of EDF scheduling when SRP is used. We find out that the overhead of job search using the conventional implementations of ready queue and job search algorithms becomes serious as the number of jobs increases. To solve this problem, we propose an alternative data structure for the ready queue and an efficient job-search algorithm with O([log$_2n$]) time complexity.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.10
• /
• pp.82-94
• /
• 2015

In this paper, we propose hardware prefetch mechanism with an efficient cache replacement policy by giving priority to the trigger block in which a spatial region and producing a spatial region by using the displacement field. It could be taken into account the sequence of the program since a history is based on the trigger block of history record, and it could be quickly prefetching the instructions or data address by adding a stored value to the trigger address and displacement field since a history is stored as a displacement value. Also, we proposed a method of replacing at random by the cache replacement policy from the low priority block when the cache area is full after giving priority to the trigger block. We analyzed using the memory simulator program gem5 and PARSEC benchmark to assess the performance of the hardware prefetcher. As a result, compared to the existing hardware prefecture to generate the spatial region using a bit vector, L1 data cache miss rate was reduced about 44.5% on average and an average of 26.1% of L1 instruction misses occur. In addition, IPC (Instruction Per Cycle) showed an improvement of about 23.7% on average.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2019.05a
• /
• pp.117-118
• /
• 2019

부산항만은 년간 천만 TEU 이상의 환적 물돌량을 처리하는 세계 2위 환적항이다. 이러한 환적 물량을 효과적으로 처리하기 위해서는 선사, 운송사, 트럭, 터미널 등 각 이해관계자간 정보의 신속하고 정확한 전달이 중요하나, 현재는 정보전달 방법이 다양하고, 정보 공유가 미흡하여 차량 대기, 정보의 누락, 터미널 혼잡 등 문제가 발생하고 있다. 이를 해결하기 위해 부산항만공사는 블록체인 기술을 활용하여 이해관계자 간에 정보를 실시간 공유함으로써 작업 우선순위를 고려한 운송계획 등을 수립할 수 있도록 하여 운송 효율을 높이기 위한 노력을 하고 있다. 본 사례 발표에서는 부산항의 ITT 관련 문제점 및 개선 방안, 향후 계획 등에 대해 논의하고자 한다.

• Journal of Digital Convergence
• /
• v.19 no.6
• /
• pp.239-250
• /
• 2021

When considering the introduction of a new technology, it is important to accurately grasp and selectively apply the technical characteristics related to the technology in order to fully utilize the advantages of the technology. In this study, the technical characteristics of high relative importance were analyzed in order to increase the efficiency of new application of blockchain technology by companies. The technical characteristics of the blockchain identified through previous research were reclassified from the perspective of the system hierarchy, and sub-factors of the technical characteristics were derived. In addition, a questionnaire survey on the relative importance of technical characteristics was conducted for internal experts and SI experts using the Analytical Hierarchy Process (AHP) technique. As a result of the analysis, respondents evaluated data protection as the most important factor in the threat of hacking related to security. In addition, it was different that the comparison results of the importance of the technical characteristics between the experts in the company and the SI experts and the priority of the technical characteristics between the expert groups by industry. It is expected that the results of this study will be usefully utilized when using blockchain technology in enterprises in line with the upcoming changes of the 4th industrial revolution. An empirical analysis of the internal and external factors required for adoption of blockchain technology by industry and the effect of technology introduction will be a meaningful study.

• Journal of the Korea Society of Computer and Information
• /
• v.29 no.7
• /
• pp.117-128
• /
• 2024

In this paper, we propose a process for deriving priority tasks using the legal design technique in a situation where there is high uncertainty in the market and legal system regarding the commercialization of security tokens based on blockchain and distributed ledger technology. To issue and distribute securities tokens, we conducted a legal design workshop with participants who applied for innovative financial services (financial regulatory sandbox). During the workshop, participants harmonized their interests and deliberated on readiness, considering both legal and technical factors. The aim was to ascertain the feasibility of identifying prioritized objectives for future endeavors. The legal design technique facilitates consensus-building among stakeholders in an uncertain environment by confirming and adjusting differing perspectives and disagreements based on mutual understanding. The key stages include the empathetic process called "Family Therapy," the "N whys" for problem definition, and the speculative scenario design for problem-solving. This approach distinguishes itself from user-centered design thinking. Given the diverse stakeholders involved, effective facilitation by the facilitator is crucial during the legal design workshop preparation and execution.

• Journal of KIISE:Computer Systems and Theory
• /
• v.28 no.8
• /
• pp.372-378
• /
• 2001

오늘날, 이질적인 분산 컴퓨팅 환경을 통합하고 분산 공유 자원을 효율적으로 사용할 수 있는 공통 작업 환경에 대한 요구가 날로 높아지고 있다. 이러한 연구 중에서 주목받는 것 중 하나가 OMG의 CORBA이다. CORBA 시스템에서 실시간 멀티미디어 데이터들을 처리하기 위해 확장된 CORBA 표준을 RT(Real-Time) CORBA라고 한다. RT CORBA의 핵심은 수많은 실시간 태스크들의 블록을 최대한 방지하여 실시간 QoS를 보장해 줄 수 있는 실시간 스케쥴링 기법에 있다고 할 수 있다. 현재 RT CORBA를 위해 제안되는 많은 스케쥴링 기법들은 대개 이전의 단일 시스템에 기반한 전역 우선순위 기반 스케쥴링이 대부분이다. 하지만 이러한 Soft Real-Time 스케쥴링은 다양한 성능 요소가 산재하는 분산 시스템에서는 그 성능을 보장할 수 없다. 본 논문에서는 CORBA와 같은 분산시스템의 보편적 특성을 고려한 Hard Real-Time 스케쥴링 기법인 CII(Cut In Interval) 기법을 제안하였다. 기존의 전역 우선순위 바탕의 스케쥴링이 비효율적인 태스크 할당 및 지역 스케쥴링을 제공하지만, CII 기법의 스케쥴링은 간단하면서도 보다 효과적인 전역 스케쥴링을 제공할 수 있다. CII 기법의 핵심은 이미 스케쥴링된 태스크를 가능한 제한시간까지 연기하여 얻어진 여유시간을 다른 실시간 태스크들의 처리에 활용하자는 것이다. 이러한 여유시간의 활용은 제안한 기법이 기존의 기법과 달리 보다 능동적이고 효율적인 스케쥴링 기법임을 증명한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2018.06a
• /
• pp.257-259
• /
• 2018

최근 JVET(Joint Video Experts Team)는 새로운 비디오 압축 표준을 VVC(Versatile Video Coding)으로 이름 짓고 2020 년 완료를 목표로 그 표준화를 시작하였다. HEVC 및 VVC 에서는 화면간 예측의 부호화 효율을 위하여 공간적/시간적 주변블록의 움직임 정보로부터 Merge/AMVP(Advanced Motion Vector Prediction)의 후보 리스트를 구성하고 최적의 움직임 정보를 활용한다. 본 논문에서는 Merge/AMVP 의 후보 리스트를 유도할 때, 현재블록의 모양을 고려하여 상관성이 높은 주변블록의 움직임 정보를 우선 순위로 유도하는 기법을 제안한다. 실험을 통하여 VTM(VVC TM) 대비 제안기법의 성능을 확인한다.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.3
• /
• pp.242-249
• /
• 2003

When special voice control application services (VCS) such as voice-controlled web browsing or voice-controlled stock transactions are introduced in cellular systems, a channel quality better than that for ordinary voice communications service (OVS) is necessary in order to keep a suitable grade of VCS. To avoid ai. congestion, calls are normally admitted if there exists a channel-processing resource not occupied by other calls in the base as well as the interference level at the receiver is not higher than a predefined threshold. The threshold is usually 10㏈ noise-rise over the background noise level for voice communications service. When the base admits VCS attempts in exactly the same manner as it handles OVS calls. the same fraction of those will be not successful in taking the channel and then blocked. If the same noise-rise threshold is used as 10 ㏈, however, the admitted VCS calls might suffer from bad channel qualify and finally be dropped. From the user's point of view, the forced termination of ongoing calls is significantly undesirable than blocking new call attempts. When using a lower noise-rise threshold for VCS. on the other hand, the blocking probability of VCS gets higher than that of OVS. In this paper, a call admission policy that gives a priority to VCS is considered in order to reduce the blocking probability and keep an adequate channel quality.