HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)

p
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 compati-
bility, 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. (However,
its effect may not be noticed until a sufficient number of new processes have been created to cause the sys-
tem 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: February 2007 − 1 − Hewlett-Packard Company 377