i want this program to be as fast as possible

[Larz60+]

you can set Linux max PID up to 2^22 (on 32 bit machine)
stored in

Output:
/proc/2497/limits

you can also use:

Output:
cat /proc/sys/kernel/pid_max

to get what it's set to
see: https://linux.die.net/man/5/limits.conf