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Date:      Fri, 20 May 2005 17:15:36 +0400
From:      Gleb Smirnoff <glebius@FreeBSD.org>
To:        Jeremie Le Hen <jeremie@le-hen.org>
Cc:        freebsd-stable@FreeBSD.org
Subject:   Re: panic in recent RELENG_5 tcp code path
Message-ID:  <20050520131536.GA30219@cell.sick.ru>
In-Reply-To: <20050520131031.GU818@obiwan.tataz.chchile.org>
References:  <20050515120007.GA777@obiwan.tataz.chchile.org> <20050518155130.H87264@carver.gumbysoft.com> <20050519125639.GK818@obiwan.tataz.chchile.org> <20050520080435.GB26938@cell.sick.ru> <20050520131031.GU818@obiwan.tataz.chchile.org>

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  Jeremie,

On Fri, May 20, 2005 at 03:10:32PM +0200, Jeremie Le Hen wrote:
J> > according to the fact that the panic occured in dereferncing mbuf pointer
J> > your kernel is compiled without INVARIANTS.
J> > 
J> > Please compile it with INVARIANTS. This will probably help to trigger panic
J> > earlier, and it will be more clear.
J> 
J> a quick look at src/conf/NOTES reveals the following :
J> %%%
J>     #
J>     # The INVARIANTS option is used in a number of source files to enable
J>     # extra sanity checking of internal structures.  This support is not
J>     # enabled by default because of the extra time it would take to check
J>     # for these conditions, which can only occur as a result of
J>     # programming errors.
J>     #
J> %%%
J> 
J> I'm going to recompile my kernel with INVARIANTS but I wonder in
J> which order of magniture it will slow my kernel down.  In other words,
J> what does INVARIANTS do concretely, shall I expect a performance drop
J> like WITNESS does ?

No. The performance loss is _much_ less significant than in WITNESS case.
You probably will not notice it.

-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE



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