mprotect_reduce_protid_on(5)mprotect_reduce_protid_on(5)NAMEmprotect_reduce_protid_on - reduces protection IDs/keys usage for
shared memory segments
VALUES
Failsafe
Default
Allowed values
or
DESCRIPTION
The tunable is provided to reduce user application's protection
IDs/keys usage for shared memory segments.
When an application uses mprotect(2) extensively on a shared memory
(shmget(2)), this may lead to a huge number of protection IDs/keys
being assigned to the application and may also increase the size of the
data structure where this information is maintained. This may result
in application performance degradation.
When the tunable is turned on, it tries to reduce the number of protec‐
tion IDs/keys being allocated to user applications. This tunable also
attempts to optimize the way the information on protection IDs/key is
maintained. Overall, using this tunable can typically help in improv‐
ing user application's performance.
However, when the tunable is turned on, there are situations when it
may not improve or may actually degrade the application's performance.
This may happen due to the overhead involved in reducing the number of
protection IDs/keys.
The overall performance depends on the nature of the application. This
tunable may work with some applications and may not work with others.
Although it attempts to improve the performance of the application, it
may result in application performance degradation or no improvement at
all.
Who Is Expected to Change This Tunable?
Anyone with super-user privileges.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Value of This Tunable Be Raised?
When you observe that the application's performance is getting degraded
due to extensive usage of mprotect(2) on shared memory segments.
What are the Side Effects of Raising the Value?
When turned on, it may sometime reduce overall system performance.
When Should the Value of This Tunable Be Lowered?
When you observe degradation when the tunable is turned on.
What are the Side Effects of Lowering the Value?
The original behavior is retained.
What Other Tunable Values Should Be Changed at the Same Time?
None.
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 HP.
SEE ALSOkctune(1M), mprotect(2), shmget(2)
Tunable Kernel Parametemprotect_reduce_protid_on(5)