How high do process IDs go these days?

[Jean-David Beyer]

Back in the old days of UNIX, process IDs used to go up only to several
hundred. As time went on, they went up to about 32767. Now with
multi-core processors on mother-boards that can take up to four
processors, they can go very high. But I am amazed at what I am seeing
these days.

I am running Red Hat Enterprise Linux release 8.2 (Ootpa) with a
4.18.0-193.28.1.el8_2.x86_64 kernel. Since I last rebooted the machine
(about a week ago), the PIDs have gone up a lot, it seems to me. The
machine seems to be operating normally, but I do run eight BOINC
processes compute-limited 24/7. I get this:
top - 00:11:02 up 8 days, 6:28, 1 user, load average: 8.24, 8.27, 8.29
Tasks: 470 total, 9 running, 461 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.2 us, 0.1 sy, 49.4 ni, 46.4 id, 3.8 wa, 0.2 hi, 0.0 si,
0.0 st
MiB Mem : 63943.9 total, 1357.9 free, 8603.4 used, 53982.6 buff/cache
MiB Swap: 15992.0 total, 15924.7 free, 67.2 used. 54533.0 avail Mem

PID PPID USER PR NI S RES SHR %MEM %CPU TIME+
566673 566654 boinc 39 19 R 1.3g 19800 2.1 99.7 2501:15
671142 671122 boinc 39 19 R 1.3g 19820 2.1 99.8 592:42.15
637068 636960 boinc 39 19 R 1.3g 19756 2.1 99.7 1219:31
691907 2079 boinc 39 19 R 761024 28688 1.2 91.8 241:20.31
682101 2079 boinc 39 19 R 760160 28688 1.2 99.7 403:18.83
681982 2079 boinc 39 19 R 575188 76092 0.9 99.8 404:55.85
702834 2079 boinc 39 19 R 230580 49832 0.4 99.7 44:35.99
701364 2079 boinc 39 19 R 113048 2640 0.2 99.7 66:23.07
2079 1 boinc 30 10 S 39320 17676 0.1 0.0 89308:04

PID1 is systemd; PID 2079 is a permanently-running daemon process, the
BOINC client that gets new work units, returns results, and schedules
the worker-processes (including starting them).

But look at those process IDs! I surely have not run that many processes
in a week. Some BOINC processes take over a week EACH.

[Melzzzzz]

Post by Jean-David Beyer
Back in the old days of UNIX, process IDs used to go up only to several
hundred. As time went on, they went up to about 32767. Now with
multi-core processors on mother-boards that can take up to four
processors, they can go very high. But I am amazed at what I am seeing
these days.
I am running Red Hat Enterprise Linux release 8.2 (Ootpa) with a
4.18.0-193.28.1.el8_2.x86_64 kernel. Since I last rebooted the machine
(about a week ago), the PIDs have gone up a lot, it seems to me. The
machine seems to be operating normally, but I do run eight BOINC
top - 00:11:02 up 8 days, 6:28, 1 user, load average: 8.24, 8.27, 8.29
Tasks: 470 total, 9 running, 461 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.2 us, 0.1 sy, 49.4 ni, 46.4 id, 3.8 wa, 0.2 hi, 0.0 si,
0.0 st
MiB Mem : 63943.9 total, 1357.9 free, 8603.4 used, 53982.6 buff/cache
MiB Swap: 15992.0 total, 15924.7 free, 67.2 used. 54533.0 avail Mem
PID PPID USER PR NI S RES SHR %MEM %CPU TIME+
566673 566654 boinc 39 19 R 1.3g 19800 2.1 99.7 2501:15
671142 671122 boinc 39 19 R 1.3g 19820 2.1 99.8 592:42.15
637068 636960 boinc 39 19 R 1.3g 19756 2.1 99.7 1219:31
691907 2079 boinc 39 19 R 761024 28688 1.2 91.8 241:20.31
682101 2079 boinc 39 19 R 760160 28688 1.2 99.7 403:18.83
681982 2079 boinc 39 19 R 575188 76092 0.9 99.8 404:55.85
702834 2079 boinc 39 19 R 230580 49832 0.4 99.7 44:35.99
701364 2079 boinc 39 19 R 113048 2640 0.2 99.7 66:23.07
2079 1 boinc 30 10 S 39320 17676 0.1 0.0 89308:04
PID1 is systemd; PID 2079 is a permanently-running daemon process, the
BOINC client that gets new work units, returns results, and schedules
the worker-processes (including starting them).
But look at those process IDs! I surely have not run that many processes
in a week. Some BOINC processes take over a week EACH.

In kernel 5.10 it is 32 bit number...