sysv_hash_locks(5)sysv_hash_locks(5)NAMEsysv_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 separate
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 mem‐
ory user needed for spinlocks but to also avoid the contention of hav‐
ing 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 con‐
tention on these locks. This could happen as a result of a very large
increase to the tunable, coupled with very heavy use of semaphore oper‐
ations.
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 sema‐
phore tunables include and Specifically, significant changes in the
number of semaphore IDs via the tunable may require changes in the tun‐
able.
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 parame‐
ter 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 val‐
ues. For information about the effects of installation on tunable val‐
ues, 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 ALSOsema(5), semaem(5), semmni(5), semmns(5), semmnu(5), semmsl(5),
semume(5), semvmx(5).
Tunable Kernel Parameters sysv_hash_locks(5)