region_hash_locks(5) [hpux man page]

region_hash_locks(5)						     OBSOLETE						      region_hash_locks(5)

NAME

       region_hash_locks - OBSOLETE kernel tunable parameter

DESCRIPTION

       The tunable is obsolete and has been removed.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 sets the size of such a pool for the region 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  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

							     Tunable Kernel Parameters					      region_hash_locks(5)

sysv_hash_locks(5)						File Formats Manual						sysv_hash_locks(5)

NAME

       sysv_hash_locks - System V IPC hashed spinlock pool size

VALUES

   Failsafe
   Default
   Allowed values
       or whichever is smaller.

       Required to be a power of two.

DESCRIPTION

       Note:  If the DynSysVSem optional product bundle is installed then this tunable is ignored and has no effect.  Each semaphore ID has a sep-
       arate lock.

       The tunable specifies the size of the hashed spinlock (kernel data structures used for synchronization) pool  (number  of  available  spin-
       locks).	 The  System  V IPC semaphore functions acquire hashed spinlocks based on the semaphore ID.  The spinlocks are hashed to avoid the
       memory user needed for spinlocks but to also avoid the contention of having just one spinlock.

       For more information about System V semaphores, refer to the section of the sema(5) manpage.

   Who Is Expected to Change This Tunable?
       Those who have identified, through kernel performance analysis, local system performance issues with these locks.  HP  experience  is  that
       very few customers need to adjust this tunable.

   Restrictions on Changing
       Changes to this tunable take effect at the next reboot.

       Note:  If the DynSysVSem optional product bundle is installed then changes to this tunable are ignored and have no effect.

   When Should the Value of This Tunable Be Raised?
       This  tunable should be raised if performance analysis shows high contention on these locks.  This could happen as a result of a very large
       increase to the tunable, coupled with very heavy use of semaphore operations.

   When Should the Value of This Tunable Be Lowered?
       If is no longer as large, and/or spinlock contention is no longer an issue.

   What Other Tunable Values Should Be Changed at the Same Time?
       All the System V semaphore tunables are interrelated and should not be treated as independent variables.  The tunables must be evaluated as
       a  system to ensure they reflect the application requirements.  The semaphore tunables include and Specifically, significant changes in the
       number of semaphore IDs via the tunable may require changes in the tunable.

       Note:  If the DynSysVSem optional product bundle is installed then the and tunables are ignored and have no effect.

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  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by AT&T.

SEE ALSO

       sema(5), semaem(5), semmni(5), semmns(5), semmnu(5), semmsl(5), semume(5), semvmx(5).

							     Tunable Kernel Parameters						sysv_hash_locks(5)