nproc(5)

NAME

nproc — limits the number of processes allowed to exist simultaneously

VALUES

Failsafe

4200

Default

4200

Allowed values

100 - 30000

This may be set higher, but more will not be used. Setting nproc below 110 will interfere with the systems ability to execute in multi-user mode. Some configurations may have a higher minimum.

nproc must be greater than nkthread + 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 will allow more processes, and lowering it will restrict the number of processes.

It can be determined that nproc is too low when the proc: table is full message is seen in the message buffer. The message buffer can be read via dmesg or syslog. 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.

It can be determined 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?

The tunable should be increased 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?

The value should be lowered 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?

Increased risk of application failure due to the inability to fork new processes.

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

nkthread must be strictly greater than nproc. Default equations ensure this, as well as runtime kernel checks.

nfile and ninode should be increased (and are not by default) to allow applications to manipulate files.

ksi_alloc_max should be increased, as the default formula is multiple of nproc.

maxuprc must be less than nproc.

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

Other tunables may require a reboot to take effect. So, dramatic increases in 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.

AUTHOR

nproc was developed by HP.