debugging kernel options (was: Re: 6.2-PRE: Fatal Trap?)

Karol Kwiatkowski freebsd at
Sat Dec 30 10:26:12 PST 2006

Robert Watson wrote:
>> P.S. out of curiosity - now that I have configured kernel with DDB and
>> KDB options, is there any performance penalty of running such kernel?
> No, it shouldn't really have any effect on performance.  The one thing
> to watch out for is that your system will no longer reboot automatically
> on a panic, as it will drop to the debugger, by default.  You can change
> this by setting debug.debugger_on_panic to 0, in which case you will
> likely want to set debug.trace_on_panic to 1 so it prints a stack trace
> before rebooting (which is often sufficient, combined with the trap
> frame and panic message to debug the problem).
> Right now these are sysctls, not tunables, but you can change the
> default using options KDB_UNATTENDED (which flips the default to not
> entering the debugger and rebooting) and options KDB_TRACE (which causes
> a trace to be printed on panic by default).  Probably they should also
> be tunables so that loader.conf entries will work.

Great explanation, thank you. I turned on debugging on my desktop
computer which, apart from normal every day use, is 'testing' STABLE by
running it :) I'm perfectly fine with the defaults, at least for now.

Cheers and thanks again,


Karol Kwiatkowski  <freebsd at orchid dot homeunix dot org>

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 250 bytes
Desc: OpenPGP digital signature
Url :

More information about the freebsd-stable mailing list