ncsize

Description

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

Starting with the Solaris 8 6/00 release, 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

Prior to the Solaris 8 6/00 release, it was difficult to determine whether the cache was too small. You could make this inference by noting the number of entries returned by kstat -n ncstats. If the number seems high, given the system workload and file access pattern, this might be due to the size of the DNLC.

Starting with the Solaris 8 6/00 release, you can use the kstat -n dnlcstats command to determine when entries have been removed from the DNLC because it was too small. The sum of the pick_heuristic and the pick_last parameters represents otherwise valid entries that were reclaimed because the cache was too small.

Excessive values of ncsize have an immediate impact on the system because the system allocates a set of data structures for the DNLC based on the value of ncsize. A system running a 32-bit kernel allocates 36-byte structures for ncsize, while a system running a 64-bit kernel allocates 64-byte structures for ncsize. The value has a further effect on UFS and NFS, unless ufs_ninode and nfs:nrnode are explicitly set.

Commitment Level

Unstable

Change History

For information, see ncsize (Solaris 10 Release).