process_id_min(5)

NAME

process_id_min — specify a minimum value for process IDs (PIDs)

VALUES

Failsafe

0

Default

0

Minimum

0

Maximum

process_id_max - 512

process_id_min must be less than or equal to process_id_max - 512. If the difference between process_id_max and process_id_min inclusive is less than nproc, nproc is effectively limited to this difference.

DESCRIPTION

The process_id_min tunable specifies the minimum process ID (PID) value to generate for new processes. It allows application developers to duplicate an environment where PID values are large for the purpose of software validation.

This tunable is primarily intended for development environments.

Who is Expected to Change This Tunable?

Anyone interested in software program validation in an environment where PIDs have large values.

Restrictions on Changing

Changes to the tunable are effective immediately. However, any existing processes and their PIDs are not changed.

It is recommended that the system be rebooted after specifying this tunable so that all PIDs in the system will have values in the selected range.

When Should the Value of This Tunable Be Raised?

Raise this tunable to validate software for tolerance of large PID values in a development environment.

What Are the Side Effects of Raising the Value?

If the difference between process_id_max and process_id_min is less than nproc, the number of processes allowed to exist simultaneously will be lower than the value of nproc.

When Should the Value of This Tunable Be Lowered?

Lower this tunable when the system is meant to be moved from a development to a production environment.

What Are the Side Effects of Lowering the Value?

If the difference between process_id_max and process_id_min is less than nproc, the number of processes allowed to exist simultaneously will be lower than the value of nproc.

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

It may be desirable to change nproc. The process_id_max tunable should, ideally, be set for the maximum value when validating software which uses PIDs. When changing process_id_min it is recommended that the system be rebooted to ensure all processes have PIDs within the desired range.

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 HP-UX kernel may silently round the selected values for process_id_max and/or process_id_min (for example, to the nearest power of 2) in order to accommodate the PID generation algorithm.

It is recommended that validation of software be carried out with the largest configurable value (1,073,741,567) for the process_id_max tunable, in conjunction with the process_id_min tunable set to something of the same magnitude (for example, 1,000,000,000).

The manpage for process_id_max (see process_id_max(5)) should be consulted for information about potential application issues with large PID values.

Because session IDs (SIDs) and process group IDs (PGIDs) are the same as the process ID of the session or group leader, an increase in the minimum PID also increases the minimum SID and PGID.

The system may assign process ID values less than process_id_min to certain special system processes.

Booting the system with process_id_min set to a non-zero value may cause the initialization process (aka init) to have a PID of something other than 1. However, most system utilities and commands will, by default, report the value of the initialization process's PID as 1. For example, getppid() returns 1 if the caller's parent is the initialization process, regardless of its actual PID.

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

process_id_min was developed by HP.