Tunable Kernel Parameters
NAME [Toc] [Back]
nproc - limits the number of processes allowed to exist simultaneously
VALUES [Toc] [Back]
Default [Toc] [Back]
Allowed values [Toc] [Back]
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 [Toc] [Back]
1000 processes per processor.
DESCRIPTION [Toc] [Back]
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 [Toc] [Back]
None. This tunable is dynamic.
When Should the Value of This Tunable Be Raised?
The tunable should be increased when running large numbers of
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
What are the Side Effects of Raising the Value?
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
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
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 [Toc] [Back]
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
AUTHOR [Toc] [Back]
nproc was developed by HP.
SEE ALSO [Toc] [Back]
ksi_alloc_max(5), maxuprc(5), nfile(5), ninode(5), nkthread(5).
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: Sep 2004 [ Back ]