PID allocation

[John Oberlander]

Im not finding this question on the forums anywhere so im going to ask. On HP-UX 11iv1 how are pids allocated, how high to they go and when are they reused? Any docs on this would be appreciated.

Thanks,
John

[James R. Ferguson]

Hi John:

The maxiumum value for a PID (MAXPID) is defined in '/usr/include/sys/param.h'.

Regards!

...JRF...

[John Oberlander]

Ok thanks! Thats a start, ill take a look at that file. But how do i get to pid's of 20000 when theres never over 5000 or so processess running? At what point to they get recirculated? Does the system use all the pids from 1-MAXPID then recycle through the free ones?

[A. Clay Stephenson · Accepted solution]

Actually the best way is to ask the kernel itself:

echo "effective_maxpid/D" | adb -k /stand/vmunix /dev/kmem

Typically the value is 30,000 --- which has been the UNIX standard for decades although some UNIX flavors go much higher. Once the effective_maxpid is reached, the pid's are recycled starting with the lowest free pid (although a few low values are reserved and thus are skipped over).

[John Oberlander]

Ah, i knew i never seen pids in the 8M's. My kernel is at 30K also. We're building a process tracking system, im pretty sure this will be enough info.

Thanks much!
John

[John Oberlander]

Closed