From: Roland Kuhn (rkuhne18.physik.tu-muenchen.de)
Date: Mon Sep 08 2003 - 09:28:59 CDT

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On Mon, 8 Sep 2003, Markus Gaugusch wrote:

> On Sep 8, mailinglists <mailinglistsbelfin.ch> wrote:
> > my primary dns server was up for 500 days. Now I see in top that it's
> > been up for only 3 days. No trace of reboot neither in messages nor in
> > last log. Does top start over at 0 if a certain amount of up-days have
> > been reached? Or how do I have to interprete that?
> I think there is an overflow at around 480 days. Look at /proc/uptime,
> maybe there is another value there.
>
Linux counts time in jiffies (usually 1/100 sec on kernel 2.4, 1/1024 sec on
2.6), and on a 32bit system this counter wraps around after 42949672.96 sec or
in other words: 497 days, 2 hours, 27 minutes and 52.96 seconds. This
'problem' is tackled in the 2.6 kernel (where it happens after about 50 days),
but it goes away as soon as you use a 64bit system...

BTW: there is a slight chance that the computer might crash during the 10msec
when jiffies==0, so you were a bit lucky that your server is still up and
running.

Ciao,
                                        Roland

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