• Journal of Computing Science and Engineering
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• v.3 no.1
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• pp.59-71
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• 2009

While the average-case performance is important for general-purpose applications, worst-case performance is crucial for real-time systems to ensure schedulability and reliability. Recent work has shown that simple prefetching techniques such as the Next-N-Line prefetching can benefit both average-case and worst-case performance; however, the improvement on the worstcase execution time (WCET) is rather limited and inefficient. This paper presents two instruction prefetching approaches that are specially designed to enhance the worst-case performance, including the loop-based prefetching and WCET-oriented prefetching. Our experiments indicate that both instruction prefetching techniques can achieve better worst-case execution cycles than the Next-N-Line prefetching while having various impacts on the average-case performance.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.226-230
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• 2008

Prefetching is one of widely used techniques to improve performance of I/O. But it has been reported that prefetching can bring adverse result on some reference pattern. This paper proposes a prefet-ching frame that can be adopted on existing prefetching techniques simply. The frame called IPRP (Improving Prefetching Effects by Exploiting Reference Patterns) and detects reference patterns online and control pre-fetching upon the characteristics of the detected pattern. In our experiment, we adopted IPRP on Linux read-ahead prefetching. IPRP could prevent adverse result clearly when Linux read-ahead prefetching increases total execution time about $40%{\sim}70%$. When Linux read-ahead prefetching could bring some benefit, IPRP with read- ahead performed similar or slightly better benefit on execution time. With this result we could see our IPRP can complement and improve legacy prefetching techniques efficiently.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.447-454
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• 2001

Various caching and prefetching algorithms have been investigated to identify and effective method for improving the performance of I/O devices. A prefetching algorithm decreases the processing time of a system by reducing the number of disk accesses when an I/O is needed. This paper proposes an AMBA prefetching method that is an extended version of the OBA prefetching method. The AMBA prefetching method will prefetching blocks continuously as long as disk bandwidth is enough. In this method, though there were excessive data request rate, we would expect efficient prefetching. And in the AMBA prefetching method, to prevent the cache pollution, it limits the number of data blocks to be prefetched within the cache area. It can be implemented in a user-level File System based on a Linux Operating System. In particular, the proposed prefetching policy improves the system performance by about 30∼40% for large files that are accessed sequentially.

• Journal of information and communication convergence engineering
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• v.12 no.3
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• pp.161-167
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• 2014

Web caches help to reduce latencies arising from slow networks through storing and reusing what was used before. Repeat access to a cached resource does not incur network latencies. However, resources that have never been used will not be found in the cache. Cache prefetching is a technique that helps to fill a cache with still-unused resources in anticipation that these resources will be used in the near future. Typically these unused resources are related to the resources that have been accessed in the recent past. While web caching exploits temporal locality, prefetching attempts to exploit spatial locality. Access to the prefetched resources will be cache hits, and therefore reduces the latency as perceived by the user. This paper reviews the cache infrastructure supported by the hypertext transfer protocol and discusses web cache prefetching in general, including Mozilla's prefetching infrastructure. It then classifies and reviews some prefetching techniques.

• Journal of Korea Multimedia Society
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• v.4 no.6
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• pp.489-499
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• 2001

This paper presents the SIC(Size-Interval-Count) prefetching system that can record the file access patterns of applications within a relatively small space of memory based on the repetitiveness of the file access patterns. The SICPS(SIC Prefetching System) is based on knowledge-based prefetching methods which includes high correctness in predicting future accesses of applications. The proposed system then uses the recorded file access patterns, referred to as "SIC access pattern information", to correctly predict the future accesses of the applications. The proposed prefetching system improved the response time by about 40% compared to the general file system and showed remarkable memory efficiency compared to the previously knowledge-based prefetching methods.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.268-270
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• 2006

모바일 기기의 성능 향상과 콘텐츠의 고품질화로 인하여 배터리 기반의 대용량 디스크 저장장치를 사용하는 모바일 임베디드 기기의 전력관리 기법이 중요한 문제가 되었다. 디스크 전력관리에 있어 prefetching을 사용하는 전력관리는 매우 유용한 방법이다. 본 논문에서는 디스크 드라이브의 전력관리를 위하여 멀티미디어 환경에서 최적의 Linux Kernel Prefetching 값을 제시한다. 이를 위하여 Prefetching이 인터랙티브 응용보다 멀티미디어 응용에서 효과적임을 보인다. 그리고 disk power state의 특성을 고려하여 모델링을 통하여 prefetching의 효용성을 평가하고 최적의 prefetching 값을 제시하며 실험을 통하여 이를 증명한다.

• Electronics and Telecommunications Trends
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• v.13 no.4 s.52
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• pp.59-69
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• 1998

The terminology of data prefetching is introduced, which includes stride, repeat distance, stall, pending stall, prefetch degree, prefetch distance, and prefetch offset. The effectiveness of hardware data prefetching in reducing cache misses is shown by presenting a square matrix multiplication example. Thereafter the pitfalls of prefetching and possible solutions are discussed.

• The Journal of Korean Institute of Next Generation Computing
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• v.14 no.5
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• pp.40-52
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• 2018

Solid state drive (SSD) cache technologies that are used as a second-tier cache between the main memory and hard disk drive (HDD) have been widely studied. The SSD cache requires a new prefetching scheme as well as cache replacement algorithms. This paper presents a prefetching scheme for a storage-class cache using SSD. This prefetching scheme is designed for the storage-class cache and based on a long-term scheduling in contrast to the short-term prefetching in the main memory. Traditional prefetching algorithms just consider only read, but the presented prefetching scheme considers both read and write. An experimental evaluation shows 2.3% to 17.8% of hit rate with a 64GB of SSD and the 4GiB of prefetching size using an I/O trace of 14 days. The proposed prefetching scheme showed significant improvement of cache hit rate and can be easily implemented in storage-class cache systems.

• Journal of KIISE:Software and Applications
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• v.35 no.3
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• pp.197-206
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• 2008

In the mobile Internet environment, frequent communications between a mobile device and a content server are required for searching or downloading learning materials. In this paper, we propose an efficient prefetching technique to reduce the network cost and to improve the communication efficiency in the mobile dictionary. Our prefetching-based approach can be explained as follows. First, we propose an overall framework for the prefetching-based mobile dictionary. Second, we present a systematic way of determining the amount of prefetching data for each of packet-based and flat-rate billing cases. Third, by focusing on the English-Korean mobile dictionary for middle or high school students, we propose an intuitive method of determining the words to be prefetched in advance. Fourth, based on these determination methods, we propose an efficient prefetching algorithm. Fifth, through experiments, we show the superiority of our prefetching-based method. From this approach, we can summarize major contributions as follows. First, to our best knowledge, this is the first attempt to exploit prefetching techniques in mobile applications. Second, we propose a systematic way of applying prefetching techniques to a mobile dictionary. Third, using prefetching techniques we improve the overall performance of a network-based mobile dictionary. Experimental results show that, compared with the traditional on-demand approach, our prefetching based approach improves the average performance by $9.8%{\sim}33.2%$. These results indicate that our framework can be widely used not only in the mobile dictionary but also in other mobile Internet applications that require the prefetching technique.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.1
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• pp.26-32
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• 2009

The multi-level storage architecture has been widely adopted in servers and data centers. However, while prefetching has been shown as a crucial technique to exploit sequentiality in accesses common for such systems and hide the increasing relative cost of disk I/O, existing multi-level storage studies have focused mostly on cache replacement strategies. In this paper, we show that prefetching algorithms designed for single-level systems may have their limitations magnified when applied to multi-level systems. Overly conservative prefetching will not be able to effectively use the lower-level cache space, while overly aggressive prefetching will be compounded across levels and generate large amounts of wasted prefetch. We design and implement a hierarchy-aware lower-level prefetching strategy called PMS(Prefetching strategy for Multi-level Storage system) that applicable to any upper level prefetching algorithms. PMS does not require any application hints, a priori knowledge from the application or modification to the va interface. Instead, it monitors the upper-level access patterns as well as the lower-level cache status, and dynamically adjusts the aggressiveness of the lower-level prefetching activities. We evaluated the PMS through extensive simulation studies using a verified multi-level storage simulator, an accurate disk simulator, and access traces with different access patterns. Our results indicate that PMS dynamically controls aggressiveness of lower-level prefetching in reaction to multiple system and workload parameters, improving the overall system performance in all 32 test cases. Working with four well-known existing prefetching algorithms adopted in real systems, PMS obtains an improvement of up to 35% for the average request response time, with an average improvement of 16.56% over all cases.