Re: About PID...???!!!

[Ray Olszewski <ray@comarre.com>]

At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
>They are assigned linearly, however once a pid is used, it is never reused
>until the machine reboots.

This is not quite correct. The pid assignment process wraps, I *think* at 
32767 (or maybe 65535). Next time around, the kernel skips over any pids 
that are still in use from the last round of assignment.

>A pid of 413 means that when that process was fork()'ed there had been 412
>other processes already created. But remember every time you type ls, you've
>run a process.
>
>413 isn't a large pid at all. My linux box which I very rarely reboot is at
>PIDs that start at 20000
>
>I'm surprised that any program you start after the boot process is as low as
>412.

Whether that is surprising or not depends on what he uses the host for and, 
naturally, on how recently it was rebooted. While my workstation is way up 
there (30180), my Linux-based router, which does not start new processes 
very much, is only at pid 828.

And, of course, there are persistent processes on any Linux host that go 
back to the boot/init process ... starting with init itself (always pid 1) 
and including long-lived daemons such as syslogd, klogd, and portmap; 
pseudo processes that are actually run in the kernel (mostly [k*] process 
names); and getty proceses listening on VTs that never get logins.



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