pfdat_hash_locks.5 (2010 09)

pfdat_hash_locks(5) pfdat_hash_locks(5)

OBSOLETE OBSOLETE

(Tunable Kernel Parameters)

NAME

pfdat_hash_locks - OBSOLETE kernel tunable parameter

DESCRIPTION

The

pfdat_hash_locks

tunable is obsolete and has been removed. HP-UX will automatically calcu-

late 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 con-

tention 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 parame-

ter 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://www.hp.com/go/hpux-core-docs

AUTHOR

pfdat_hash_locks

was developed by HP.

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pfdat_hash_locks(5) pfdat_hash_locks(5) OBSOLETE OBSOLETE (Tunable Kernel Parameters) NAME pfdat_hash_locks - OBSOLETE kernel tunable parameter DESCRIPTION The pfdat_hash_locks tunable is obsolete and has been removed.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.
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(Notes) A (Notes) pA 2 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010