• Journal of IKEEE
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• v.23 no.1
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• pp.80-90
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• 2019

Even though Non-Volatile Memory (NVM) is used for data storage, a page table should be built to access data in it. And this observation leads us to the Persistent Page Table (PPT) scheme that keeps the page table in NVM persistently. By the way, processors have different page table structures and really operational page table cannot be built without virtual and physical addresses of NVM. However, those addresses are determined dynamically when NVM storage is attached to the system. Thus, the PPT should have system-independent and also address-independent structure and really working system-dependent page table should be built from the PPT. Moreover, entries of PPT should be updated atomically and, in this paper, we describe the design of PPT that meets those requirements. And we investigate how file systems can decrease the journaling overhead with the swap operation, which is a new operation created by the PPT. We modified the Ext4 file system in Linux and experiments conducted with Filebench workloads show that the swap operation enhances file system performance up to 60%.

• Journal of KIISE
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• v.43 no.5
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• pp.524-530
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• 2016

The desire to access data faster and the growth of next-generation memories such as non-volatile memories, contribute to the development of research on memory file systems. It is recommended that memory mapped file I/O, which has less overhead than read-write I/O, is utilized in a high-performance memory file system. Memory mapped file I/O, however, brings a page table overhead, which becomes one of the big overheads that needs to be resolved in the entire file I/O performance. We find that same overheads occur unnecessarily, because a page table of a file is removed whenever a file is opened after being closed. To remove the duplicated overhead, we propose the mapping cache, a technique that does not delete a page table of a file but saves the page table to be reused when the mapping of the file is released. We demonstrate that mapping cache improves the performance of traditional file I/O by 2.8x and web server performance by 12%.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.15-18
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• 2003

Flash memory becomes more important for its fast access speed, low-power, shock resistance and nonvolatile storage. But its native restrictions that have limited 1ifetime, inability of update in place, different size unit of read/write and erase operations need to managed by FTL(Flash Translation Layer). FTL has to control the wear-leveling, address mapping, bad block management of flash memory. In this paper, we focuses on the fast access to address mapping table and proposed the way of faster valid page search in the flash memory using the VPLT(Valid Page Lookup Table). This method is expected to decrease the frequency of access of flash memory that have an significant effect on performance of read and block-transfer operations. For the validations, we implemented the FTL based on Windows CE platform and obtained an improved result.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.478-482
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• 2006

This paper implemented speech-library and the Web Services that conversion the Web page for the speech recognition. The system is consisted of Web services consumer and Web services providers. The Web services consumer has libraries that Speech-library and proxy-library. The Speech -library has functions as follows from the user's speech extracted speech-data and searching the URL in link-table that is mapped with user's speech. The proxy-library calls two web services and is received the returning result. The Web services provider consisted of Parsing Web Services and Speech-Recognition Web Services. Parsing Web Services adds ActiveX control and reconstructs web page using the speech recognition. The speech recognizer is the web service providers that implemented in the previous study. As the result of experiment, we show that reconstructs web page and creates link-Table. Also searching the URL in link-table that is mapped with user's speech. Also confirmed returning the web page to user by searching URL in link-table that is mapped with the result of speech recognition web services.

• International Journal of Contents
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• v.11 no.2
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• pp.15-19
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• 2015

In this paper, we propose an efficient document layout analysis algorithm that includes table detection. Typical methods of document layout analysis use the height and gap between words or columns. To correspond to the various styles and sizes of documents, we propose an algorithm that uses the mean value of the distance transform representing thickness and compare with components in the local area. With this algorithm, we combine a table detection algorithm using the same feature as that of the text classifier. Table candidates, separators, and big components are isolated from the image using Connected Component Analysis (CCA) and distance transform. The key idea of text classification is that the characteristics of the text parallel components that have a similar thickness and height. In order to estimate local similarity, we detect a text region using an adaptive searching window size. An improved adaptive run-length smoothing algorithm (ARLSA) was proposed to create the proper boundary of a text zone and non-text zone. Results from experiments on the ICDAR2009 page segmentation competition test set and our dataset demonstrate the superiority of our dataset through f-measure comparison with other algorithms.

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.11-18
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• 2021

The flash translation layer(FTL) of SSD maps the logical page number requested from the host to the actual recorded flash memory page number. It is very important to reduce the amount of RAM used to manage the mapping information. In the existing demand-based FTLs, two-level method is applied in which mapping information is also recorded in flash memory pages and only their addresses are managed as a table in RAM. As the capacities of SSDs are growing to tens of terabytes, the amount of RAM for mapping table becomes too large. In this paper, ML-FTL was proposed as a method of managing mapping information in three levels to reduce the amount of RAM required drastically. From an evaluation, the increase in overhead was minimal compared to the conventional two-level method by properly utilizing cache.

• Journal of the Korea Society of Computer and Information
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• v.20 no.5
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• pp.1-12
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• 2015

NAND flash memory has being used for storage systems widely, because it has good features which are low-price, low-power and fast access speed. However, NAND flash memory has an in-place update problem, and therefore it needs FTL(flash translation layer) to run for applications based on hard disk storage. The FTL includes complex functions, such as address mapping, garbage collection, wear leveling and so on. Futhermore, implementation of the FTL on low-power embedded systems is difficult due to its memory requirements and operation overhead. Accordingly, many index data structures for NAND flash memory have being studied for the embedded systems. Overall performances of the index data structures are enhanced by a decreasing of page write counts, whereas it has increased page read counts, as a side effect. Therefore, we propose an index management method using a page mapping log table in $B^+$-Tree based on NAND flash memory to decrease page write counts and not to increase page read counts. The page mapping log table registers page address information of changed index node and then it is exploited when retrieving records. In our experiment, the proposed method reduces the page read counts about 61% at maximum and the page write counts about 31% at maximum, compared to the related studies of index data structures.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.103-105
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• 2011

그림자 페이지테이블(shadow page table)은 MMU 를 가상화 함으로써 게스트 운영체제들이 하드웨어에서 제공하는 물리 메모리를 실제로 사용하는 것처럼 보이도록 하는 기술로 전가상화 지원 ARM 기반 가상머신 모니터인 ViMo 역시 게스트 운영체제간의 메모리 격리를 위해서 그림자 페이지 테이블을 사용한다. 본 논문에서는 그림자 페이지테이블의 성능을 향상시키기 위하여 ViMo에서 사용하는 그림자테이블에 지연 동기화 기법을 추가하는 방법에 대해 설명하고 성능상의 이점을 보인다.

• Journal of Digital Contents Society
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• v.11 no.1
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• pp.91-97
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• 2010

Flash memory has been used by many digital devices for data storage, exploiting the advantages of non-volatility, low power, stability, and so on, with the help of high integrity, large capacity, and low price. As the fast growing popularity of flash memory, the density of it increases so significantly that its entire address mapping table becomes too big to be stored in SRAM. This paper proposes the associated page address cache with an efficient table management scheme for hybrid flash translation layer mapping. For this purpose, all tables are integrated into a map block containing entire physical page tables. Simulation results show that the proposed scheme can save the extra memory areas and decrease the searching time with less 2.5% of miss ratio on PC workload and can decrease the write overhead by performing write operation 33% out of total writes requested.

• Journal of KIISE:Software and Applications
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• v.31 no.9
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• pp.1180-1195
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• 2004

Due to the exponential increase of information, search and access for the Web information or service takes much time. Web information is represented through several web pages using hyperlinks and each web page is contains several topics. However. most existing web tools don't reflect such web authoring tendencies and treat it as an independent information unit. This inconsistency yields inherent problems in web browsing and searching. In this paper, we propose a web surfing assistant called LinkBroker that provides collodion pages. They are composed of relevant information extracted from several web pages that have table and frame structure in order to improve accessibility to web information. Especially, the system extracts a set of web pages that are logically connected and groups those pages using table and frame tags. Then, essential information blocks in each page of a group are extracted to construct an integrated summary page. It Provides a comprehensive view to user and one cut way to access distributed information. Experimental results show the effectiveness and usefulness of LinkBroker system.