NAME
ncsize — number of Directory Name Lookup Cache (DNLC) entries
VALUES
Allowed values
The minimum value allowed is
128.
The maximum value allowed is memory limited.
The value is further constrained in that it must be equal to or greater than
eight times the value of the number of locks for the DNLC
(ncsize >= 8 * dnlc_hash_lock).
Specify a positive integer value.
DESCRIPTION
To speed up the search through directories in the kernel, there is a memory
resident cache
of directories called the
Directory Name Lookup Cache (DNLC).
During a filename lookup in the kernel, any directories or files encountered are retained
in the DNLC for future reference.
The
ncsize
tunable dictates the number of entries in the DNLC,
which is statically allocated at system boot time.
Therefore, the larger the value of
ncsize,
the larger the number of directory/file entries that can be kept
cached in memory for filename lookup.
Who Is Expected to Change This Tunable?
HP-UX system administrators.
Restrictions on Changing
This tunable is static.
Any changes to the value of this tunable will require system reboot before taking effect.
When Should the Value of This Tunable Be Raised?
The value may need to be raised to improve filename lookup performance
when running applications which require large numbers of filename access.
What are the Side Effects of Raising the Value?
More system memory will be consumed for the DNLC.
When Should the Value of This Tunable Be Lowered?
The value can be lowered to limit the number of entries in the DNLC and
reduce memory consumption.
What are the Side Effects of Lowering the Value?
Less system memory will be consumed for the DNLC upon system reboot.
Operations requiring filename lookup (e.g. open(2)) may
experience performance degradation.
What Other Tunable Values Should Be Changed at the Same Time?
The value of
ncsize
must be equal to or greater than
eight times the value of
dnlc_hash_locks
(ncsize >= 8 * dnlc_hash_lock).
WARNINGS
All HP-UX kernel tunable parameters are release specific.
This parameter may be removed or have its meaning changed in
future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors,
may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or
recommended values. For information about the effects of
installation on tunable values, consult the documentation
for the kernel software being installed.
For information about optional kernel software that was
factory installed on your system, see
HP-UX Release Notes
at
http://docs.hp.com.
AUTHOR
ncsize
was developed by HP.
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