sysv_hash_locks(5) [hpux man page]

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)

semmns(5)							File Formats Manual							 semmns(5)

NAME

       semmns - number of System V IPC system-wide semaphores

VALUES

   Failsafe
   Default
   Allowed values
DESCRIPTION

       The  tunable  specifies the maximum total individual System V IPC system-wide semaphores which can be assigned by applications.	Semaphores
       are assigned in "sets" associated with an ID.  Thus semaphores can be distributed in any manner across the range of IDs with  one  or  more
       per ID.

       There is no reason to specify less than (the maximum number of identifiers) as each ID requires at least one semaphore.

       If an application attempts to create a semaphore set with more semaphores than are remaining, it will receive an error from

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

   Who Is Expected to Change This Tunable?
       Anyone.

   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 take effect immediately.

   When Should the Value of This Tunable Be Raised?
       If applications require more total semaphores in the system.

   When Should the Value of This Tunable Be Lowered?
       If requirements for semaphores has decreased, or there is a need to hard-limit applications from acquiring larger numbers of semaphores.

   What Are the Side Effects of Lowering the Value?
       The following side effect applies only if the DynSysVSem optional product bundle is installed.

       If  DynSysVSem  is  installed,  lowering the value of this tunable increases the risk of application failure due to the inability to create
       more semaphore sets.  Lowering the tunable has no effect on any active semaphores in their respective sets, even if the new  tunable  value
       is  less  than  the  number of semaphores already created on the system.  However, no new semaphore sets may be created until the number of
       active semaphores on the system falls below the setting of

   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 Typically, a change in the tunable does
       not require changes to other tunables.

       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

       semget(2), sema(5), semaem(5), semmni(5), semmnu(5), semmsl(5), semume(5), semvmx(5), sysv_hash_locks(5).

							     Tunable Kernel Parameters							 semmns(5)