• Journal of KIISE
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• v.41 no.11
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• pp.871-877
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• 2014

Cache replacement algorithms have been developed in order to reduce miss counts. In modern processors, the performance gap between the processor and main memory has been increasing, creating a more important role for cache replacement policies. The Least Recently Used (LRU) policy is one of the most common policies used in modern processors. However, recent research has shown that the performance gap between the LRU and the theoretical optimal replacement algorithm (OPT) is large. Although LRU replacement has been proven to be adequate over and over again, the OPT/LRU performance gap is continuously widening as the cache associativity becomes large. In this study, we observed that there is a potential chance to improve cache performance based on existing LRU mechanisms. We propose a method that enhances the performance of the LRU replacement algorithm based on the access proportion among the lines in a cache set during a period of two successive replacement actions that make the final replacement action. Our experimental results reveals that the proposed method reduced the average miss rate of the baseline 512KB L2 cache by 15 percent when compared to conventional LRU. In addition, the performance of the processor that applied our proposed cache replacement policy improved by 4.7 percent over LRU, on average.

• Journal of the Korea Society of Computer and Information
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• v.25 no.3
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• pp.11-17
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• 2020

In this paper, we propose practical results for cache replacement policy by measuring cache hit and search time for each replacement algorithm through cache simulation. Thus, the structure of each cache memory and the four types of alternative policies of FIFO, LFU, LRU and Random were implemented in software to analyze the characteristics of each technique. The paper experiment showed that the LRU algorithm showed hit rate and search time of 36.044% and 577.936ns in uniform distribution, 45.636% and 504.692ns in deflection distribution, while the FIFO algorithm showed similar performance to the LRU algorithm at 36.078% and 554.772ns in even distribution and 45.662% and 489.574ns in bias distribution. Then LFU followed, Random algorithm was measured at 30.042% and 622.866ns at even distribution, 36.36% at deflection distribution and 553.878ns at lowest performance. The LRU replacement method commonly used in cache memory has the complexity of implementation, but it is the most efficient alternative to conventional alternative algorithms, indicating that it is a reasonable alternative method considering the reference information of data.

• Journal of the Korea Society of Computer and Information
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• v.18 no.11
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• pp.1-12
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• 2013

In multi-core processors, Last Level Cache(LLC) can reduce the speed gap between the memory and the core. For this reason, LLC has big impact on the performance of processors. LLC is composed of shared cache and private cache. In computer architecture community, most researchers have mainly focused on the management techniques for shared cache, while management techniques for private cache have not been widely researched. In conventional private LLC, memory is statically assigned to each core, resulting in serious performance degradation when the workloads are not fairly distributed. To overcome this problem, this paper proposes the replacement policy for managing private cache of LLC efficiently. As proposed core-aware cache replacement policy can reconfigure LLC dynamically, hit rate of LLC is increases drastically. Moreover, proposed policy uses 2-bit saturating counters to improve the performance. According to our simulation results, the proposed method can improve hit rates by 9.23% and reduce the access time by 12.85% compared to the conventional method.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.86-91
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• 2022

Cache bypassing is a scheme to prevent unnecessary cache blocks from occupying the capacity of the cache for avoiding cache contamination. This method is introduced to alleviate the problems of non-volatile memories (NVMs)-based memory system. However, the prior works have been studied without considering wear-out attack. Malicious writing to a small area in NVMs leads to the failure of the system due to the limited write endurance of NVMs. This paper proposes a novel scheme to prolong the lifetime with higher resistance for the wear-out attack. First, the memory reference pattern is found by modified reuse distance calculation for each cache block. If a cache block is determined as the target of the attack, it is forwarded to higher level cache or main memory without updating the NVM-based cache. The experimental results show that the write endurance is improved by 14% on average and 36% on maximum.

• The Journal of the Korea Contents Association
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• v.4 no.3
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• pp.71-80
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• 2004

In distributed file-systems, cooperative caching algorithm which owns the data cached at each node jointly is used to reduce an expense of disk access. Cooperative caching algorithm is the method that increases a cache hit-ratio and decrease a disk access as it holds the cache information of distributed systems in common and makes cache larger virtually. Recently, several cooperative caching algorithms decrease the message costs by using approximate information of the cache and increase the cache hit-ratio by using local and global cache fields dynamically. And they have an advantage that increases the whole field hit-ratio by sending a replaced buffer to the idle node on buffers replacement in order to maintain the replaced cache in the cache field. However the wrong approximate information deteriorates the performance, the consistency maintenance goes to great expense to exchange messages and the cost that manages Age-information of each node to choose the idle node increases. In this thesis, we propose a cooperative cache algorithm that maintains correct cache information, minimizes the maintenance cost for consistency and the management cost for buffer Age-information. Also, we show the superiority of our algorithm through the performance evaluation.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.961-968
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• 2002

This paper proposes a new access method which is to considered the high variability in World Wide Web and manage the web cache space. Instead of using a single cache, we divide a cache and store all documents according to their file types. Proposed method was compares with current cache management policies using LFU, LRU and SIZE base algorithm. Using two different workload, we show the improvement hitting ratio and byte hitting ratio through simulating on the file type caching.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2202-2211
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• 2006

EXT3NS is a special-purpose file system for large scale multimedia streaming servers. It is built on top of streaming acceleration hardware device called Network-Storage card. The EXT3NS file system significantly improves streaming performance by eliminating memory-to-memory copy operations, i.e. sending video/audio from disk directly to network interface with no main memory buffering. In this paper, we design and implement a buffer cache mechanism, called PMEMCACHE, for EXT3NS file system. We also propose a buffer cache replacement method called ONS for the buffer cache mechanism. The ONS algorithm outperforms other existing buffer replacement algorithms in distributed multimedia streaming environment. In EXT3NS with PMEMCACHE, operation is 33MB/sec and random read operation is 2.4MB/sec. Also, the buffer replacement ONS algorithm shows better performance by 600KB/sec than other buffer cache replacement policies. As a result PMEMCACHE and an ONS can greatly improve the performance of multimedia steaming server which should supportmultiple client requests at the same time.

• Journal of KIISE:Databases
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• v.27 no.1
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• pp.53-63
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• 2000

The mobile computing service market is increasing rapidly due to the development of low-cost wireless network technology and the high-performance mobile computing devices. In recent years, several methods have been proposed to effectively deal with restrictions of the mobile computing environment such as limited bandwidth, frequent disconnection and short-lived batteries. Amongst those methods, much study is being done on the caching method - among the data transmitted from a mobile support station, it selects those that are likely to be accessed in the near future and stores them in the local cache of a mobile host. Existing cache replacement methods have some limitations in efficiency because they do not take into consideration the characteristics of user mobility and spatial attributes of geographical data. In this paper, we show that the value and the semantic of the data, which are stored in the cache of a mobile host, changes according to the movement of the mobile host. We argue it is because data that are geographically near are better suited to provide an answer to a users query in the mobile environment. Also, we define spatial location of geographical data has effect on, using the spatial attributes of data. Finally, we propose two new cache replacement methods that efficiently support user mobility and spatial attributes of data. One is based on the location of data and the other on the meaningful region of data. From the comparative analysis of the previous methods and that they improve the cache hit ratio. Also we show that performance varies according to data density using this, we argue different cache replacement methods are required for regions with varying density of data.

• Journal of the Korea Society of Computer and Information
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• v.16 no.3
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• pp.89-97
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• 2011

In semantic web information system like ontology that access distributed information from network, efficient query processing requires an advanced caching mechanism to reduce the query response time. P2P network system have become an important infra structure in web environment. In P2P network system, when the query is initiated, reducing the demand of data transformation to source peer is important aspect of efficient query processing. Caching of query and query result takes a particular advantage by adding or removing a query term. Many of the answers may already be cached and can be delivered to the user right away. In web environment, semantic caching method has been proposed which manages the cache as a collection of semantic regions. In this paper, we propose the semantic caching technique in cluster environment of peers. Especially, using schema data filtering technique and schema similarity cache replacement method, we enhanced the query processing efficiency.

• Journal of KIISE:Databases
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• v.28 no.4
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• pp.688-701
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• 2001

Web caching has become an important problem addressing the performance issues in web applications. In this paper we propose a method that enhances the performance of web caching by incorporating the expiration time of web data we introduce the notion of the effective reference probability that incorporates the effect of expiration time into the reference probability used in the existing cache replacement algorithms .We formally define the effective reference probability and derive it theoretically using a probabilistic model. By simply replacing probabilities with the effective reference probability in the existing cache replacement algorithms we can take the effect of expiration time into account The results of performance evaluation through experiments show that the replacement algorithms using the effective reference probability always outperform the existing ones. The reason is that the proposed method precisely reflects the theoretical probability of getting the cache effect, and thus, incorporates the influence of the expiration time more effectively. In particular when the cache fraction is 0.05 and data update is comparatively frequent (i.e. the update frequency is more than 1/0 of the reference frequency) the performance enhancement is more than 30% in LRU-2 and 13% in Aggarwal's method (PSS integrating a refresh overhead factor) The results show that effective reference probability contributes significantly to the performance enhancement of the web cache in the presence of expiration time.