• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.4-6
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• 2004

본 논문에서는 원격 캐쉬를 추가시킨 분산 메모리 구조 다중 프로세서 시스템의 성능 향상을 위해 새로운 원격 캐쉬 교체 정색을 제안한다. 일반적으로 다중 계층 내포성(MLI)을 치키는 다중 계층 메모리 구조에서 LRU 교체 정책을 사용할 경우, 상위 계층 캐쉬의 LRU 정보와 하위 계층 캐쉬의 LRU 정보가 서로 상이함으로 인해 하위 계층 캐쉬에서의 교체가 상위 계층에서 사용 중인 캐처 라인의 교체를 발생시켜 전체 시스템의 성능을 저하시키는 원인이 된다. 이러한 LRU 캐쉬 교체 정책의 단점을 보완하고자 각 노드 당 프로세서들의 원격 메모리 접근 지역성을 이용한 원격 캐쉬 교체정책의 사용으로 상위 캐쉬의 유용한 캐쉬 라인의 접근 실패율을 감소시킴으로써 다중 프로세서 시스템의 성능 향상을 꾀한다. 프로그램 기반 시뮬레이터를 통해 제안한 원격 캐쉬 교체 정책을 적용하였을 때, 기존의 LRU 교체 정책과 비교하여 무효화 수와 캐쉬 접근 실패가 평균 5%. 최대 10% 감소하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.92-95
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• 2019

CDN은 여러 서버에 데이터를 분산하여 캐시 한 뒤 빠르게 데이터를 배포하는 네트워크이다. 하지만 CDN은 서버 성능에 영향을 받고 데이터의 Lifetime이 얼마 없는 경우 중앙 서버 혹은 데이터 제작자와의 통신을 통해 데이터를 새로 받아야 한다. 반면에, NDN은 데이터를 라우터별로 캐시하여 트래픽을 분산시키고 딜레이를 줄였다. 하지만, 캐시 된 데이터의 Lifetime에 따라 데이터를 받지 못하는 문제가 있다. 본 논문에선 데이터 요청자가 Lifetime 내에 데이터를 못 받으면 요청자의 네트워크 상황과 Interest 패킷의 주기를 고려하여 캐시 된 데이터의 Lifetime을 증가시켜 안정성 있는 데이터 배포를 목표로 하였다. 캐시 정책이 적용된 시뮬레이션을 진행했으며, 얼마 남지 않은 Lifetime을 증가시켜 데이터 요청자가 데이터를 온전히 받을 수 있음을 확인하였다.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.1-6
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• 2022

Modern computer systems usually have special hardware for operations used in deep learning workload even edge computing environment. Non-volatile memories (NVMs) have been considered for alternative memory storage because they consume little static energy and occupy small area. However, there is a problem for NVMs to be directly adopted. An NVM cell has limited write endurance, so that the lifetime of NVM-based memory system is much shorter than that of conventional memory system. To overcome this problem for the deep learning system, this paper proposes a novel method to extend the lifetime based on the analysis of the deep learning workloads. If an incoming block has more than a predefined number of frequently used values, the cacheline is defined as write friendly block. During the victim selection, the cacheline has lower possibility to be chosen as victim. The experimental results show that the lifetime is increased by about 50% and energy consumption is decreased by 3% with a little performance hurt.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.19-27
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• 2015

Due to the advantages of fast read/write operation and low power consumption, SSD(Solid State Drive) is now widely adopted as storage device of smart phone, laptop computer, server, etc. However, the shortcomings of SSD such as limited number of write operations and asymmetric read/write operation lead to the problem of shortened life span of SSD. Therefore, the block replacement policy of SSD used as cache for HDD is very important. The existing solutions for improving the lifespan of SSD including the LARC scheme typically employ the LRU algorithm to manage the SSD blocks, which may increase the miss rate in SSD due to the replacement of frequently used block instead of rarely used block. In this paper we propose a novel block replacement scheme which considers the block reuse interval to effectively handle various data read/write patterns. The proposed scheme replaces the block in SSD based on the recency decided by reuse interval and age along with hit ratio. Computer simulation using workload trace files reveals that the proposed scheme consistently improves the performance and lifespan of SSD by increasing the hit ratio and decreasing the number of write operations compared to the existing schemes including LARC.

• Journal of KIISE:Databases
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• v.32 no.1
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• pp.56-70
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• 2005

The results of location-dependent queries(LDQ) generally depend on the current locations of query issuers. Many mechanisms, e.g. broadcast scheme, hoarding, or racking policy, have been developed to improve the system peformance and provide better services, which are specialized for LDQs. Considering geographical adjacency of data and characteristics oi target area, caching policy and broadcast scheme affect the overall performance in LDQ. For this reason, we propose both the caching policy and broadcast scheme, which these features are reflected in. Based on the adjacency of data in LDQ, our broadcast scheme use Hilbert curve to cluster data. Moreover, in order to develop the caching policy suitable for LDQ on urban area, we apply the moving distance of a MH(Mobile Host) to our caching policy We evaluate the performance of the caching policy measuring the workload of MHs and the correctness of LDQ results and the performance of the broadcast scheme measuring the average setup-time of MHs in our experiments. Finally, we expect that our caching policy Provides more correct answers when executing LDQ in focal cache and leads significant improvement of the performance of MHs. It also seems quite probable that our broadcast scheme leads improvement of battery life of the MH.

• Transactions on Electrical and Electronic Materials
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• v.13 no.5
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• pp.256-261
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• 2012

Recently, many photovoltaic systems (PV systems) including solar parks and PV farms have been built to prepare for the post fossil fuel era. To investigate the degradation process of the PV systems and thus, efficiently operate PV systems, there is a need to visually monitor PV systems in the range of infrared ray through the Internet. For efficient visual monitoring, this paper explores a multithreaded implementation of a recently developed HEVC standard whose compression efficiency is almost two times higher than H.264. For an efficient parallel implementation under a meshbased 64 multicore system, this work takes into account various design choices which can solve potential problems of a two-dimensional interconnects-based 64 multicore system. These problems may have not occurred in a small-scale multicore system based on a simple bus network. Through extensive evaluation, this paper shows that, for an efficient multithreaded implementation of HEVC intra prediction in a mesh-based multicore system, much effort needs to be made to optimize communications among processing cores. Thus, this work provides three design choices regarding communications, i.e., main thread core location, cache home policy, and maximum coding unit size. These design choices are shown to improve the overall parallel performance of the HEVC intra prediction algorithm by up to 42%, achieving a 7 times higher speed-up.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.199-206
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• 2012

Increment of mobile client's information request in wireless mobile networks requires a new method to manage and serve the streaming media object. This paper proposes a new object segment grouping method for enhancing the performance of streaming media services in wireless mobile networks. The proposed method performs the similarity metric for the partitioned object segments, and it process the disjunction, conjunction, and filtering for these metrics. This paper was to decided the partitioned group of object segments for these operation metrics, and it decided the performance of streaming media services. The simulation result showed that the proposed method has better performance in throughput, average startup latency, and cache hit ratio.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.61-63
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• 2005

분산 메모리에 기반한 다중 프로세서 시스템은 기존의 중앙 집중형 메모리 구조의 단점인 메모리 접근의 병목현상을 극복하고 프로세서와 메모리의 부가에 따라 메모리 대역폭을 확장시킬 수 있는 구조로써 최근의 다중 프로세서 시스템 구조의 주류로 대두되고 있다. 다중 프로세서 시스템의 성능은 메모리 접근 지연에 의하여 제한 받고 있는데 이러한 이유는 프로세서의 동작 주파수 속도에 비하여 메모리의 접근 지연이 수십 배 이상이 되기 때문이다. 특히 분산 메모리 다중 프로세서 시스템에 있어서 메모리 접근은 지역 메모리 접근과 원격 메모리 접근의 두 가지 유형으로 나눌 수 있는데 이 중 원격 메모리 접근 지연은 시스템의 상호 접속망 구조에 따라 지역 메모리 접근 지연에 비하여 수 배 내지 수십 배에 이르고 있다. 본 논문에서는 분산 메모리 다중 프로세서 시스템에서 상호 접속 망의 구조에 따라 원격 메모리 접근 간에도 시간 지연의 차이가 있음에 착안하여 원격 메모리 접근 시간 지연에 따른 최적화 된 원격 캐시 관리 정책을 제시하며 각 상호 접속 망의 구조에 따라 이러한 캐시 관리 정책에 의한 성능 향상의 정도를 측정한다.

• The KIPS Transactions:PartA
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• v.19A no.1
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• pp.35-44
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• 2012

Traditional technologies that are used to improve the performance of hard disk drives show many negative cases if they are applied to solid state drives (SSD). Access time and block sequence in hard disk drives that consist of mechanical components are very important performance factors. Meanwhile, SSD provides superior random read performance that is not affected by block address sequence due to the characteristics of flash memory. Practically, it is recommended to disable prefetching if a SSD is installed in a personal computer. However, this paper presents a combinational method of a prefetching scheme and a memory management that consider the internal structure of SSD and the characteristics of NAND flash memory. It is important that SSD must concurrently operate multiple flash memory chips. The I/O unit size of NAND flash memory tends to increase and it exceeded the block size of operating systems. Hence, the proposed prefetching scheme performs in an operating unit of SSD. To complement a weak point of the prefetching scheme, the proposed memory management scheme adaptively evicts uselessly prefetched data to maximize the sum of cache hit rate and prefetch hit rate. We implemented the proposed schemes as a Linux kernel module and evaluated them using a commercial SSD. The schemes improved the I/O performance up to 26% in a given experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9B
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• pp.610-618
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• 2005

As developed Internet and Computer Capability, Many Users take the many information through the network. So requirement of User that use to network was rapidly increased and become various. But it spend much time to accept user requirement on current network, so studied such as Active network for solved it. This Active node on Active network have the capability that stored and processed execution code aside from capability of forwarding packet on current network. So required execution code for executed packet arrived in active node, if execution code should not be in active node, have to take by request previous Action node and Code Server to it. But if this execution code take from previous active node and Code Server, bring to time delay by transport execution code and increased traffic of network and execution time. So, As used execution code stored in cache on active node, it need to increase execution time and decreased number of request. So, our paper suggest ANC caching technique that able to decrease number of execution code request and time of execution code by efficiently store execution code to active node. ANC caching technique may decrease the network traffic and execution time of code, to decrease request of execution code from previous active node.