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mprotect_reduce_protid_on(5)			  mprotect_reduce_protid_on(5)

NAME
       mprotect_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 ALSO
       kctune(1M), mprotect(2), shmget(2)

			   Tunable Kernel Parametemprotect_reduce_protid_on(5)

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