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semmsl.5 (2010 09)

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semmsl(5) semmsl(5)
(Tunable Kernel Parameters)
NAME
semmsl - maximum number of System V IPC semaphores per identifier
VALUES
Failsafe
2048
Default
2048
Allowed values
Minimum: 1
Maximum: 10240
DESCRIPTION
The semmsl tunable specifies the maximum number of individual System V IPC semaphores per sema-
phore identifier (ID).
If an application attempts to exceed this limit, it will receive an [EINVAL] error from
semget().
For more information about System V semaphores, refer to the Overview section of the sema(5) manpage.
Who Is Expected to Change This Tunable?
Anyone.
When Should the Value of This Tunable Be Raised?
If applications require a larger number of semaphores per ID.
When Should the Value of This Tunable Be Lowered?
If application requirements for semaphores per ID has decreased or there is a need to protect against ill-
behaved applications.
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 vari-
ables. The tunables must be evaluated as a system to ensure they reflect the application requirements.
The semaphore tunables include
semaem, semmni, semmns, semmnu, semmsl, semume, semvmx
, and
sysv_hash_locks. Specifically, a change in the
semmsl tunable may require a change in the
semmns tunable.
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.
Prior to HP-UX 11i Version 1 the maximum number of semaphores per ID was an undocumented constant
2048 in the header file sys/sem.h. Typically applications do not depend upon this limitation. For those
that were compiled with the old constant, semmsl tunable values higher than 2048 will generally not be
a problem. However, semmsl tunable values lower than 2048 may cause other such applications to fail.
These should be recoded to obtain the current semmsl value from pstat_getipc (2).
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
semmsl was developed by AT&T.
SEE ALSO
kctune(1M), semget(2), sema(5), semaem(5), semmns(5), semmni(5), semmnu(5), semume(5), semvmx(5),
sysv_hash_locks(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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