wraparound value for time

[Dan Nelson]

In the last episode (Mar 22), Chris Landauer said:
> i am running some very long programs, and it appears that time wraps
> around in its counting (the 72 cpu hour program did not wrap, the 164
> cpu hour program did)

Which value wrapped?  user, system, or elapsed?
 
> i tried to figure out where the actual code for time is, but i can't
> quite tell - it appears to be buried inside csh somewhere (it also
> appears that there are several different possibilities for the data
> type used, depending on some compile time parameters for the csh
> compilation)

The best I could come up with was that elapsed time might be stored in
a long variable in milliseconds, which would wrap at 49.7 days.  User
and system times are stored as "struct timeval"s and should never wrap.

> finally, can anybody tell me what the default tick size is? or
> better, where i can look to find out?

"sysctl kern.clockrate" has that info.  Hz defaults to 100, and tick is
1000000 / hz = 10000.  You can adjust Hz by setting kern.hz in
/boot/loader.conf.

-- 
	Dan Nelson
	dnelson at allantgroup.com