A page replacement method for nand flash memory

Abstract

The present invention discloses an NAND flash memory-oriented page replacement method, belonging to the field of data storage. According to the method, a cold clean page linked list and another hybrid page linked list respectively manage cold clean pages and other cache pages, and a reserved ghost page linked list records metadata information of recent obsolete cache pages; before page visit processing, initialization is performed first, if the page is hit in another hybrid page linked list or the cold clean page linked list, the page is marked a hot page and is moved to a recently visited terminal of another hybrid page linked list; if the page is hit in the ghost page linked list, record of the page in the ghost page linked list is deleted, a new cache page is allocated to the page and is marked a hot page, and the page is moved to the recently visited terminal of another hybrid page linked list; and finally, if it is determined that the page is read or write request, the data is read or written in the cache page and is returned. Through adoption of the method, flash memory write operation is reduced, and a higher cache hit ratio is maintained as far as possible.

Description

technical field [0001] The invention belongs to the field of data storage, and more specifically relates to a page replacement method for NAND flash memory. Background technique [0002] NAND flash memory (flash memory) is a non-volatile storage medium proposed by Toshiba Corporation in 1989, which has the advantages of high performance, high density, good shock resistance, and low power consumption. Therefore, NAND flash memory is widely used in embedded devices, portable computers. With the rapid development of NAND flash memory technology, it is also widely used in enterprise-level storage systems. For simplicity, the flash memory mentioned later in this article defaults to NAND flash memory unless otherwise specified. [0003] Cache plays an extremely important role in the storage system. By storing hot data in a small-capacity cache, the performance of the storage system can be significantly improved. For decades, researchers have proposed various page replacement al...

AI Technical Summary

Problems solved by technology

However, these algorithms still have their own problems

For example, CFLRU does not fully consider the access frequency of cached pages, which may cause cold and clean pages to be unable to be replaced out of the cache in time, resulting in cache pollution

CCFLRU and PTLRU replace clean pages in a more aggressive way. However, they can easily cause hot clean pages to not be identified and stored in the cache, which may lead to a significant drop in hit rate, which will impair the final I / O performance.

In summary, the existing various cache page replacement algorithms have the above-mentioned defects and cannot improve the I / O performance of flash-based storage systems very well.

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