NAME
dnlc_hash_locks — number of locks for the Directory Name Lookup Cache (DNLC)
VALUES
Allowed values
The minimum value allowed is
16.
The maximum value allowed is
8192.
The value is further constrained in that
it must be be a power of 2, and it must be equal to or less than
one-eighth the number of DNLC entries
(ncsize >= 8 * dnlc_hash_locks).
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 DLNC is managed in a Least Recently Used
(LRU)
fashion.
The
dnlc_hash_locks
dictates the number of lock groups that will be used to manage
the directory entries in the DNLC hash chains.
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
require a system reboot before taking effect.
When Should the Value of This Tunable Be Raised?
The value may need to be raised to reduce lock contention
and improve filename lookup performance
when running applications which require large numbers of file name accesses.
What are the Side Effects of Raising the Value?
More system memory will be consumed to allocate locks for the DNLC.
When Should the Value of This Tunable Be Lowered?
The value can be lowered to limit the number of locks allocated for the DNLC
and to reduce memory consumption.
What are the Side Effects of Lowering the Value?
Less system memory will be consumed for the DNLC locks upon system reboot.
Operations requiring filename lookup (for example,
open()
(see
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_locks).
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
dnlc_hash_locks
was developed by HP.
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