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Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007

Technical documentation

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rtsched_numpri — number of priority values to support for POSIX.1b realtime applications






Allowed Values

Any value in the range of 32 to 512 is allowed. A value lower than 32 is reset to 32, whereas a value higher than 512 is reset to 512.

Recommended Value



The rtsched_numpri tunable defines how many priority values to support for POSIX 1.b realtime applications. A larger value provides additional flexibility to applications in managing relative priorities of all threads with respect to each other and with respect to other applications running in the system. However, a larger value adds processing overhead in the operating system in terms of managing larger run queues with the possibility of increased search times.

Who Is Expected to Change This Tunable?


Restrictions on Changing

Changes to this tunable take effect at next reboot.

When Should the Value of This Tunable Be Raised?

When the system is primarily running POSIX realtime applications, and requires additional flexibility in managing relative priorities of applications.

What Are the Side Effects of Raising the Value?

Raising the value of the rtsched_numpri tunable may cause some operating system overhead due to larger and possibly more sparse run queues.

When Should the Value of This Tunable Be Lowered?

The default value of the rtsched_numpri tunable is already set to the minimum possible value.

What Other Tunable Values Should Be Changed at the Same Time?



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.

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 http://docs.hp.com.


rtsched_numpri was developed by HP.

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