Dynamic buffer cache management scheme based on simple and aggressive prefetching

Abstract

Many replacement and prefetching policies have recently been proposed for buffer cache management. However, many real operating systems, including GNU/Linux, generally use the simple Least Recently Used (LRU) replacement policy with prefetching being employed in special situations such as when sequentiality is detected. In this paper, we propose the SAW 2R scheme that integrates buffer management and prefetching, where prefetching is done constantly in aggressive fashion. The scheme is simple to implement making it a feasible solution in real systems. In its basic form, for buffer replacement, it uses the LRU policy. However, its modular design allows for any replacement policy to be incorporated into the scheme. For prefetching, it uses the LRU-One Block Lookahead (LRU-OBL) approach, eliminating any extra burden that is generally necessary in other prefetching approaches. Implementation studies based on the GNU/Linux kernel version 2.2.14 show that the SA-W2R performs better than the current version of GNU/Linux with a maximum increases of 23 % for the workloads considered.