wraparound value for time
Dan Nelson
dnelson at allantgroup.com
Tue Mar 23 08:59:27 PST 2004
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
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