DNLC Improvements

The directory name look-up cache (DNLC) is enhanced to provide improved performance when you access files in large directories with 1000 or more files.

The DNLC is a general file system service that caches the most recently referenced directory names and their associated vnodes. UFS directory entries are stored linearly on disk, which means that locating an entry requires searching each entry for the name. The addition of a new entry requires searching the entire directory to ensure that the name does not exist. To solve this performance problem, the DNLC caches entire directories in memory.

Another feature in this release is the DNLC caching of file objects that have been looked up, but do not exist. This feature is known as negative caching, and is useful because some applications repeatedly test to check if a file exists.

For more information, see Solaris Tunable Parameters Reference Manual.