ncsize Parameter

Description

Defines the number of entries in the directory name look-up cache (DNLC). This parameter is used by UFS, NFS, and ZFS to cache elements of path names that have been resolved.

The DNLC also caches negative look-up information, which means it caches a name not found in the cache.

Data Type

Signed integer

Default

(4 x (v.v_proc + maxusers) + 320) + (4 x (v.v_proc + maxusers) + 320) / 100

Range

0 to MAXINT

Units

DNLC entries

Dynamic?

No

Validation

None. Larger values cause the time it takes to unmount a file system to increase as the cache must be flushed of entries for that file system during the unmount process.

When to Change

You can use the kstat -n dnlcstats command to view the number of hits and misses in the DNLC. A high ratio of misses to hits might indicate that the DNLC is too small. Increasing the value of ncsize can help improve performance.

Excessive values of ncsize have an immediate impact on the system memory usage. Memory that is used directly by the DNLC increases in proportion to ncsize. In addition, caching more entries in the DNLC might require filesystem context relating to those entries to remain in memory when it would otherwise be freed.

Commitment Level

Unstable