On my 2.6.7 kernel (no tweaks to this value):
> cat /proc/sys/kernel/pid_max 32768
Since I'd expect databases to align such stuff to 32 bit anyway, I think a 2^32 is a safe bet. And using this virtual file will give you the correct answer for the current system.
Ref: proc(5):
/proc/sys/kernel/pid_max
This file (new in Linux 2.5) specifies the value at which PIDs
wrap around (i.e., the value in this file is one greater than
the maximum PID). The default value for this file, 32768,
results in the same range of PIDs as on earlier kernels. The
value in this file can be set to any value up to 2^22
(PID_MAX_LIMIT, approximately 4 million).Cheers,
--Amos
Michael Kraus wrote:
G'day...
I'm developing a database application that uses the inserting processes
pid. Problem is that I'm wondering how big this pid should be?
(OK, if I was a true guru, I'd know this magic number off the top of my
head...)
Is the maximum value of a pid on a UN*X system 65,535? (At least
generally speaking - I think on FreeBSD for example its at 30,000 by
default.)
I've been looking at a lot of web pages, but mostly they seem to deal
with the maximum number of concurrent processes. (Which is rather
defined by memory and sits at about 33,000 for modified Linux with an
average process -excluding the OS-being 30K, but only 4,090 unmodified.)
Regards,
Michael S. E. Kraus
Software Developer/Technical Support Specialist
Wild Technology Pty Ltd
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