NAME
pfdat_hash_locks — OBSOLETE kernel tunable parameter
DESCRIPTION
The
pfdat_hash_locks
tunable is obsolete and has been removed.
HP-UX will automatically calculate the value
based on the system configuration.
Global kernel structures containing information on a running process
or memory usage are frequently accessed or modified by several
threads concurrently.
To prevent race conditions, these structures are protected by spinlocks
(kernel data used for synchronization) which allow only the spinlock
"holder" to proceed, while all others attempting to access the
structure must wait.
Hashed spinlocks are used when each instance of such a data structure
is to be protected, and there are several instances.
Using a single spinlock for all instances would cause too much
contention, but using one spinlock per structure wastes memory
while the majority of the locks are unused at any given time.
By allocating a pool of hashed locks, a hash function picks one
lock per group of structures, reducing contention while conserving
memory.
The system-calculated value of
pfdat_hash_locks
sets the size of such a pool for the pfdat data structure spinlocks.
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
pfdat_hash_locks
was developed by HP.