nproc(5)

NAME

nproc — limits the number of processes allowed to exist simultaneously

VALUES

Failsafe

4200

Default

4200

Allowed values

100 - 60000

The system may allow settings higher than 60,000 but such values are unsupported. Setting nproc below 110 interferes with the system's ability to execute in multi-user mode. Some configurations may have a higher minimum.

nkthread must be greater than nproc + 100.

nproc must be greater than maxuprc + 5.

Recommended values

1000 processes per processor.

DESCRIPTION

The nproc tunable controls the absolute number of processes allowed on a system at any given time. Increasing it allows more processes, and lowering it restricts the number of processes.

You can determine that nproc is too low when the proc: table is full message is seen in the message buffer. Use dmesg or syslog to read the message buffer. This message indicates that an application was unable to create a new process. Setting nproc too low can cause application failures due to an inability to fork new processes.

You can determine how many processes have been used simultaneously by calling pstat_dynamic and examining the psd_numprocsallocd. This field indicates the "high water" mark of the number of processes that have been simultaneously used.

Who Is Expected to Change This Tunable?

Anyone expecting to run large numbers of processes.

Restrictions on Changing

None. This tunable is dynamic.

When Should the Value of This Tunable Be Raised?

Increase the value of nproc when running large numbers of processes simultaneously.

What are the Side Effects of Raising the Value?

None.

When Should the Value of This Tunable Be Lowered?

Lower the value only to limit the number of processes on the system, or when there is memory pressure and the value of nproc is far above the expected usage.

What are the Side Effects of Lowering the Value?

Lowering the value increases the risk of application failure due to the inability to fork new processes.

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

Increase nkthread to ensure there are sufficient threads for each process.

Adjust ksi_alloc_max, as the default formula is multiple of nproc.

A single user may not consume all processes on the system (see maxuprc).

Some of these other tunables used to adjust automatically. These adjustments must now be made explicitly.

Other tunables may require a reboot to take effect. So, dramatic increases in the value of nproc without reboot should be made with caution.

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.

The effective number of processes allowed to exist simultaneously may be affected by the values of the tunables process_id_max and process_id_min.

Some applications may have been coded with a built-in assumption that the number of processes cannot exceed 30,000, which was the maximum imposed by prior versions of HP-UX. Such applications may fail on configurations which allow and/or create more than 30,000 processes.

The HP-UX kernel creates internal data structures optimized for the value of the nproc tunable parameter at boot time. After significant changes to the tunable it is recommended that a reboot be scheduled so that the kernel can reoptimize these internal data structures.

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.

AUTHOR

nproc was developed by HP.