panic in recent RELENG_5 tcp code path

Dan Nelson dnelson at
Fri May 20 11:55:58 PDT 2005

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 
> > J> words, what does INVARIANTS do concretely, shall I expect a 
> > J> performance drop like WITNESS does ?
> > 
> > No. The performance loss is _much_ less significant than in WITNESS
> > case. You probably will not notice it.
> Actually, INVARIANTS causes about a 10% penalty on wall clock time on
> 5.x and above.

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.

	Dan Nelson
	dnelson at

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