process_id_max.5 (2010 09)

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process_id_max(5) process_id_max(5)

(Tunable Kernel Parameters)

NAME

process_id_max - limit the maximum value for process IDs (PIDs)

VALUES

Failsafe

30000

Default

30000

Minimum

process_id_min + 512

Maximum

1,073,741,823

process_id_max

must be greater than or equal to process_id_min + 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_max tunable allows the administrator to select a potential value range for process IDs

(PIDs) as generated by fork (see fork (2)). It allows the administrator to select a balance between com-

patibility, capacity, and aesthetics.

Warning: Some programs cannot tolerate PID values up to the maximum. If such programs exist and

are critical, the maximum PID should be appropriately constrained. For more details on these concerns,

see Potential Application Issues, below.

Who is Expected to Change This Tunable?

Anyone.

Restrictions on Changing

Do not increase the maximum PID if there are critical applications which assume that PIDs ﬁt into a res-

tricted range. (See WARNINGS , below).

The value of

process_id_max

can be increased at any time, and it takes effect immediately. (How-

ever, its effect may not be noticed until a sufﬁcient number of new processes have been created to cause

the system to utilize the available higher values.)

A decrease in the value of

process_id_max

also takes effect immediately. However any existing

processes with PIDs that are higher than the new value are not affected. The decrease will be in full

effect for all processes only after a reboot.

When Should the Value of This Tunable Be Raised?

Increase the maximum PID if the range of PIDs deﬁned by the

process_id_min and

process_id_max tunables needs to be increased to allow the creation of more simultaneous processes.

See nproc (5) for limits on the number of processes.

Increase the maximum PID in systems which have many active processes (for example, >25,000). The

larger range may increase the efﬁciency of creating of new processes (because it may take less work to

ﬁnd available PIDs).

If it is desired to validate that software programs execute properly in environments where PID values

may be large, increase the

process_id_max tunable along with the process_id_min

tunable to

force all new process IDs to take on large values. (See process_id_min(5) for more information.)

Do not increase the maximum PID if there are critical applications which assume that PIDs ﬁt into a res-

tricted range. (See WARNINGS below.)

What are the Side Effects of Raising the Value?

If the difference between

process_id_max and process_id_min tunables is less than nproc, the

number of processes allowed to exist simultaneously is limited to that difference.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
process_id_max(5) process_id_max(5) (Tunable Kernel Parameters) NAME process_id_max - limit the maximum value for process IDs (PIDs) VALUES Failsafe 30000 Default 30000 Minimum process_id_min + 512 Maximum 1,073,741,823 process_id_max must be greater than or equal to process_id_min + 512. If the difference between process_id_max and process_id_min inclusive is less than nproc, nproc is effectively limited to this difference.
PAGE 2
process_id_max(5) process_id_max(5) (Tunable Kernel Parameters) When Should the Value of This Tunable Be Lowered? Lower the maximum PID if critical applications make assumptions that the PID range is restricted. What are the Side Effects of Lowering the Value? If the difference between process_id_max and process_id_min tunables is less than nproc, the number of processes allowed to exist simultaneously is limited to that difference.