Linux Kernel Development, Third Edition

16. The Page Cache and Page Writeback

The Linux kernel implements a disk cache called the page cache. The goal of this cache is to minimize disk I/O by storing data in physical memory that would otherwise require disk access. This chapter deals with the page cache and the process by which changes to the page cache are propagated back to disk, which is called page writeback.

Two factors comingle to make disk caches a critical component of any modern operating system. First, disk access is several orders of magnitude slower than memory access—milliseconds versus nanoseconds. Accessing data from memory rather than the disk is much faster, and accessing data from the processor’s L1 or L2 cache is faster still. Second, data accessed once will, with ...