Cost-based buffer area replacement method of flash memory database

Abstract

The invention discloses a cost-based buffer area replacement method of a flash memory database. The method comprises the following steps of: classifying data pages in a buffer area and endowing weight values; and during buffer area replacement, selecting a replacement page according to weight values of the data pages. Compared with the other buffer area replacement methods of a database system based on flash memories, the invention has the advantages that: by the method, adaptive strategy adjustment can be carried out according to the flash memories with different functions, so the method can be applied to different flash memory hard disks and better performance can be obtained. On the premise of no reduction of a hit rate, proper replacement pages are fairly selected from a read-only queue or a modification queue according to the weight values of the data pages, so the write operation of the flash memories can be reduced, the abrasion of the flash memories is reduced, and the performance of the system is improved. By the method, a sequence access mode and a long cyclic access mode can be well processed, so compared with other buffer area management methods provided based on the flash memories, the method provided by the invention has the advantages that: better performance can be obtained, and the method can be applied to various flash memories and various access modes.

Description

technical field [0001] The invention relates to a buffer replacement method, in particular to a cost-based flash memory database buffer replacement method. Background technique [0002] A typical computer system contains two layers of memory, namely main memory (buffer) and auxiliary memory (external storage media, such as disk or SSD). The access speed of the buffer is much faster than that of the auxiliary storage, and the two generally use data pages of the same size. [0003] When the system needs to operate a data page, the buffer algorithm needs to prepare the required data page for the system according to the following steps: [0004] (1) Check whether the requested page is in the current buffer. [0005] (2) If the requested page is in the current buffer, obtain the required data directly and end. [0006] (3) Otherwise, select a replacement page according to a certain strategy. [0007] (4) If the replacement page is a read-only page, read the requested page dir...

AI Technical Summary

Problems solved by technology

[0025] However, the main disadvantages of the above methods are: 1. The buffer strategy designed for disk assumes that all physical operations on auxiliary storage have the same storage cost, so it cannot take advantage of the fast read speed of flash memory and cannot avoid the cost of flash write operations 2. The buffer strategy designed for flash memory assumes that the cost of reading flash memory is negligible compared with the cost of expensive write operations, which is inconsistent with the actual situation

3. The buffer strategy designed for flash memory does not consider the difference in the asymmetry of read and write costs of different flash memories, but only designs a buffer strategy for a certain flash memory

4. The buffer strategy designed for flash memory does not consider the problem that the replacement cost of different data pages is different

Images