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. DNLC caches the most recently referenced directory names and their associated vnodes. UFS directory entries are stored linearly on disk. This means that locating an entry requires searching each entry for the name. Adding a new entry requires searching the entire directory to ensure the name does not exist. To solve this performance problem, entire directories are cached in memory by the DNLC.

Another feature in this release is that DNLC caches 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.

New tunable parameters are associated with the DNLC improvements. These parameters are set optimally. Do not change the parameters casually.

See the Solaris Tunable Parameters Reference Manual for further information.