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Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007

Technical documentation

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region_hash_locks — OBSOLETE kernel tunable parameter


The region_hash_locks tunable is obsolete and has been removed. HP-UX will automatically calculate its 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 structures 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 region_hash_locks sets the size of such a pool for the region data structure spinlocks.


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.


region_hash_locks was developed by HP.

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