• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.546-553
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• 2015

Recently, flash cache is widely adopted as the performance accelerator of legacy storage systems. Unlike other cache media, flash cache should be carefully managed as it has peculiar characteristics such as long write latency and limited P/E cycles. In particular, we make two prominent observations that can be utilized in managing flash cache. First, a serious worn-out problem happens when the working-set of a system is beyond the capacity of flash cache due to excessively frequent cache replacement. Second, more than 50% of data has no hit in flash cache as it is a second level cache. Based on these observations, we propose a cache admission control policy that does not cache data when it is first accessed, and inserts it into the cache only after its second access occurs within a certain time window. This allows the filtering of data disruptive to flash cache in terms of endurance and performance. With this policy, we prolong the lifetime of flash cache 2.3 times without any performance degradations.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.188-193
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• 2022

The energy efficiency of memory systems is an important task in designing future computer systems as memory capacity continues to increase to accommodate the growing big data. In this article, we present an energy-efficient last-level cache management policy for future mobile systems. The proposed policy makes use of low-power PCM (phase-change memory) as the main memory medium, and reduces the amount of data written to PCM, thereby saving memory energy consumptions. To do so, the policy keeps track of the modified cache lines within each cache block, and replaces the last-level cache block that incurs the smallest PCM writing upon cache replacement requests. Also, the policy considers the access bit of cache blocks along with the cache line modifications in order not to degrade the cache hit ratio. Simulation experiments using SPEC benchmarks show that the proposed policy reduces the power consumption of PCM memory by 22.7% on average without degrading performances.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4912-4933
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• 2015

Information Centric Networking (ICN) has recently attracted great attention. It names the content decoupling from the location and introduces network caching, making the content to be cached anywhere within the network. The benefits of such design are obvious, however, many challenges still need to be solved. Among them, the local caching policy is widely discussed and it can be further divided into two parts, namely the cache permission policy and the cache replacement policy. The former is used to decide whether an incoming content should be cached while the latter is used to evict a cached content if required. The Internet is a user-oriented network and popular contents always have much more requests than unpopular ones. Caching such popular contents closer to the user's location can improve the network performance, and consequently, the local caching policy is required to identify popular contents. However, considering the line speed requirement of ICN routers, the local caching policy whose complexity is larger than O(1) cannot be applied. In terms of the replacement policy, Least Recently Used (LRU) is selected as the default one for ICN because of its low complexity, although its ability to identify the popular content is poor. Hence, the identification of popular contents should be completed by the cache permission policy. In this paper, a cache permission policy called Cache-Filter, whose complexity is O(1), is proposed, aiming to store popular contents closer to users. Cache-Filter takes the content popularity into account and achieves the goal through the collaboration of on-path nodes. Extensive simulations are conducted to evaluate the performance of Cache-Filter. Leave Copy Down (LCD), Move Copy Down (MCD), Betw, ProbCache, ProbCache⁺, Prob(p) and Probabilistic Caching with Secondary List (PCSL) are also implemented for comparison. The results show that Cache-Filter performs well. For example, in terms of the distance to access to contents, compared with Leave Copy Everywhere (LCE) used by Named Data Networking (NDN) as the permission policy, Cache-Filter saves over 17% number of hops.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.11_12
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• pp.541-556
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• 2005

The memory access latency of the system has been a primary factor of performance degradation in single-processor system and multi-processor system. The remote memory access latency takes a lot of overhead over the local memory access latency especially in the distributed shared-memory system. To resolve this problem, the multi-level cache architecture that contains a remote cache in the multi-processor system has been proposed. In this paper, we propose a new cache replacement policy that improves the performance of the multi-processor system with the remote cache. If the multi-level cache keeps the multi-level inclusion(MLI) property and uses the LRU(Least Recently Used) cache replacement policy, the LRU information of the higher-level cache(a processor cache) would be different with that of the lower-level cache(a remote cache). In this situation, the replacement of a remote cache line can induce the exchange of a processor cache line that is used by the processor. It is a main factor of performance degradation in a whole system. To alleviate this disadvantage of the LRU replacement polity, the new policy analyses tht processor's remote memory access pattern of each node and uses this information to reduce the number of invalidations of the useful cache line in the higher-level cache. The new replacement policy of the remote cache can improve the performance by $3.5\%$ in maximum and $2.5\%$ in average on SPLASH-2 benchmarks, compared to the general LRU cache replacement policy.

• International journal of advanced smart convergence
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• v.11 no.2
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• pp.1-6
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• 2022

With the emergence of the new era of the 4th industrial revolution, compute-bound workloads with large memory footprint like big data processing increase dramatically. Even in such compute-bound workloads, however, we observe bulky I/Os while loading big data from storage to memory. Although file I/O cache plays a role of accelerating the performance of storage I/O, we found out that the cache hit rate in such environments is not improved even though we increase the file I/O cache capacity because of some special I/O references generated by compute-bound workloads. To cope with this situation, we propose a new file I/O cache management policy that improves the cache hit rate for compute-bound workloads significantly. Trace-driven simulations by replaying file I/O reference logs of compute-bound workloads show that the proposed cache management policy improves the cache hit rate compared to the well-acknowledged CLOCK algorithm by a large margin.

• ETRI Journal
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• v.35 no.4
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• pp.687-696
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• 2013

The development of proxy caching is essential in the area of video-on-demand (VoD) to meet users' expectations. VoD requires high bandwidth and creates high traffic due to the nature of media. Many researchers have developed proxy caching models to reduce bandwidth consumption and traffic. Proxy caching keeps part of a media object to meet the viewing expectations of users without delay and provides interactive playback. If the caching is done continuously, the entire cache space will be exhausted at one stage. Hence, the proxy server must apply cache replacement policies to replace existing objects and allocate the cache space for the incoming objects. Researchers have developed many cache replacement policies by considering several parameters, such as recency, access frequency, cost of retrieval, and size of the object. In this paper, the Weighted-Rank Cache replacement Policy (WRCP) is proposed. This policy uses such parameters as access frequency, aging, and mean access gap ratio and such functions as size and cost of retrieval. The WRCP applies our previously developed proxy caching model, Hot-Point Proxy, at four levels of replacement, depending on the cache requirement. Simulation results show that the WRCP outperforms our earlier model, the Dual Cache Replacement Policy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1091-1101
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• 2015

Cache mechanism, which has been a research subject for a significant period of time in computer science, has become realized in the form of web caching in network practice. Web caching has various advantages, such as saving of network resources and response time reduction, depends its performance on cache replacement policy, therefore, analysis and consideration of the environment in which a web cache operates is essential for designing better replacement policies. Thus, in the current web environment where is rapidly changing relative to the past, a new cache replacement policy is necessary to reflect those changes. In this paper we stipulate some characteristics of the web at present, propose a new cache replacement policy, and evaluate it.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.10
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• pp.556-568
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• 2003

This paper presents and analyzes the performance of a weighted-window based cache replacement policy for the efficient media caching in streaming media cache servers. The proposed policy makes, for each cached object, use of the reference count, reference time, amount of media delivered to clients and, in particular, the periodic patterns of user requests. Also, by giving weights to the recently referenced media contents, the replacement policy adequately and swiftly reflects the ever-changing characteristics of users preferences. The simulation studies show that the performance of the proposed policy has improved over the conventional policies such as LRU, LFU and SEG - in terms of hit ratio, byte hit ratio, delayed start and cache input.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.8
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• pp.473-486
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• 2004

NUMA systems have remote access caches(RAC) in each local node to reduce the overhead for repeated remote memory accesses. By this RAC, memory latency and network traffic can be reduced and the performance of the multiprocessor system can be improved. Until now, several cache replacement policies have been proposed in recent years, and there also is cache replacement policy for multiprocessor systems. In this paper, we propose a cache replacement policy which is based on cache line coherence information. In this policy, the cache line that does not have an ownership is replaced first with respect to cache line that has an ownership. Like this way, the overhead to transfer ownership is avoided and the memory latency can be decreased. We also propose “Keeping-Ownership replacement policy with MRU (KOM)” and “Keeping-Ownership replacement policy with Reference Bit(KORB)” to reduce the frequent replacement penalty of the ownership-lacking cache line. We compare and analyze these with LRU and Pseudo LRU(PLRU). The simulation shows that KOM outperforms the PLRU by 25%, and KORB outperforms the PLRU by 13%. Although the hardware cost of KOM is very small, the performance of KOM is nearly equal to that of the LRU.

• Journal of Korea Game Society
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• v.3 no.1
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• pp.67-73
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• 2003

Most web caches save documents temporarily into themselves on the basis of those documents. And when a corresponding document exists within the cache on wei s request, web cache sends the document to corresponding user. On the contrary, when there is not any document within the cache, web cache requests a new document to the related server to copy the document into the cache and then rum it back to user. Here, web cache uses a replacement policy to change existing document into a new one due to exceeded capacity of cache. Typical replacement policy includes document-based LRU or LFU technique and other various replacement policies are used to replace the documents within cache effectively. However, these replacement policies function only with regard to the time and frequency of document request, not considering the popularity of each web site. Based on replacement policies with regard to documents on frequent requests and the popularity of each web site, this paper aims to present the document replacement policies with regard to the popularity of each web site, which are suitable for latest network environments to enhance the hit-ratio of cache and efficiently manage the contents of cache by effectively replacing documents on intermittent requests by new ones.