Getting started with DTrace in FreeBSD-current (a.k.a. 8)

John Birrell jb at
Thu Jun 12 21:52:30 UTC 2008

On Thu, Jun 12, 2008 at 11:38:50PM +0200, Diego Depaoli wrote:
> 2008/6/11 John Birrell <jb at>:
> >
> > It's been a few weeks now since I committed DTrace support to current.
> I'm curious... impact over performances?

DTrace is supposed to be low impact until you enable probes. When you enable
probes, the impact depends on how many probes, how often they are called
and what the actions do.

> kern_dtrace.o(.text+0x1e0): first defined here
> ld: Warning: size of symbol `kdb_enter' changed from 34 in
> kern_dtrace.o to 70 in subr_kdb.o
> *** Error code 1

Try removing the #ifndef and the code it contains in kern_dtrace.c.
It looks like the kdb_enter function is always compiled in.

John Birrell

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