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Date: Fri, 20 May 2005 15:10:32 +0200
From: Jeremie Le Hen <jeremie@le-hen.org>
To: Gleb Smirnoff <glebius@FreeBSD.org>
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cc: Jeremie Le Hen <jeremie@le-hen.org>
cc: freebsd-stable@FreeBSD.org
Subject: Re: panic in recent RELENG_5 tcp code path
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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 >