The Directory Cache

Another important cache that is maintained on Unix systems is the directory cache, on System V this is known as the Directory Name Lookup Cache (DNLC) on Linux it is called the D cache.

The directory cache contains a list of the most recently accessed file and directory names mapped to inode numbers it also acts as a controller for an inode cache of recently used inodes.

The directory cache on Linux grows and shrinks dynamically in user memory like the buffer cache.