Tunable Kernel Parameters
NAME [Toc] [Back]
semmsl - maximum number of System V IPC semaphores per identifier
VALUES [Toc] [Back]
Default [Toc] [Back]
Allowed values [Toc] [Back]
DESCRIPTION [Toc] [Back]
The semmsl tunable specifies the maximum number of individual System V
IPC semaphores per semaphore 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?
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 variables. 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 [Toc] [Back]
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
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
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
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 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
AUTHOR [Toc] [Back]
semmsl was developed by AT&T.
SEE ALSO [Toc] [Back]
semget(2), sema(5), semaem(5), semmns(5), semmni(5), semmnu(5),
semume(5), semvmx(5), sysv_hash_locks(5).
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