panic in recent RELENG_5 tcp code path

[Jeremie Le Hen]

Hi Gleb,

> according to the fact that the panic occured in dereferncing mbuf pointer
> your kernel is compiled without INVARIANTS.
> 
> Please compile it with INVARIANTS. This will probably help to trigger panic
> earlier, and it will be more clear.

a quick look at src/conf/NOTES reveals the following :
%%%
    #
    # The INVARIANTS option is used in a number of source files to enable
    # extra sanity checking of internal structures.  This support is not
    # enabled by default because of the extra time it would take to check
    # for these conditions, which can only occur as a result of
    # programming errors.
    #
%%%

I'm going to recompile my kernel with INVARIANTS but I wonder in
which order of magniture it will slow my kernel down.  In other words,
what does INVARIANTS do concretely, shall I expect a performance drop
like WITNESS does ?

Best regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >