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Date: Fri, 20 May 2005 11:57:03 -0700
From: Kris Kennaway <kris@obsecurity.org>
To: Dan Nelson <dnelson@allantgroup.com>
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cc: Kris Kennaway <kris@obsecurity.org>
Subject: Re: panic in recent RELENG_5 tcp code path
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On Fri, May 20, 2005 at 01:55:56PM -0500, Dan Nelson wrote:
> In the last episode (May 20), Kris Kennaway said:
> > On Fri, May 20, 2005 at 05:15:36PM +0400, Gleb Smirnoff wrote:
> > > On Fri, May 20, 2005 at 03:10:32PM +0200, Jeremie Le Hen wrote:
> > > 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=20
> > > J> words, what does INVARIANTS do concretely, shall I expect a=20
> > > J> performance drop like WITNESS does ?
> > >=20
> > > No. The performance loss is _much_ less significant than in WITNESS
> > > case. You probably will not notice it.
> >=20
> > Actually, INVARIANTS causes about a 10% penalty on wall clock time on
> > 5.x and above.
>=20
> Which is a lot less of a hit than WITNESS is, to be sure.  WITNESS is
> like walking in mud :)  Do you know if INVARIANT_SUPPORT by itself is
> enough to cause the 10% slowdown?  That turns on LOCK_DEBUG, which in
> turn disables inlining of mutex macros.

I haven't benchmarked that, but it would be interesting to know.

Kris

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