Why kernel.pid_max = 4194304 on my system?

vikrantchaudhary21

"For historical reasons, the largest PID has been limited to a 16-bit number, or 32768. But for some reason on my system the kernel.pid_max = 4194304 . How that possible.

coop

Because you are on a 64 bit system and using a more recent kernel. The sentence could use more elatboration.

r9:/home/coop>ps 
    PID TTY          TIME CMD
  54249 pts/2    00:00:00 bash
  80648 pts/2    00:00:00 ps
r9:/home/coop>cat /proc/sys/kernel/pid_max 
4194304
r9:/home/coop>

Note that 4194304=4*1024*1024, or 2^24 I don't know the historical specifics that made it this many bits.

vikrantchaudhary21

Thanks for answering.

cocobongo

I'm currently running on OpenSUSE Tumbleweed with kernel 6.3.7-1-default (as per uname -a) on a 64-bit machine, but I still see the specified 32768 max_pid. Is the bit architecture relevant to this or perhaps the distribution maintainers are responsible for keeping this variable at a lower value?

coop

Probably a distro thing, or the way they configure their kernel

cocobongo

Thank you for clarifying that!