is dtrace usable?

[Alexander Leidinger]

On Sat, 6 Mar 2010 15:09:51 +0000 (GMT) Robert Watson
<rwatson at FreeBSD.org> wrote:


> 
> On Sat, 6 Mar 2010, Daniel Braniss wrote:
> 
> > 	link_elf_obj: symbol lapic_cyclic_clock_func undefined
> >
> > when trying
> > 	kldload dtraceall this is with a fearly resent 8-stable
> >
> > I'm trying to help Rick Maclem debug the NSF/UDP problem, and I
> > thought it would be a good chance to learn dtrace, but :-(
> 
> Take a look at the DTrace configuration information here:
> 
>    http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/dtrace.html

I've just reread it (despite the fact that I already used it). Some
comments:

Last time I tried, I didn't see any problems by adding
  makeoptions     WITH_CTF=yes
to the kernel config instead of doing
  make WITH_CTF=1 kernel

Did I miss something, and if not, shouldn't we tell about the
makeoptions part instead (a kernel rebuild later will not cause
trouble when someone forgets to do the WITH_CTF part as it is already
in the kernel makefile)?

What is DDB_CTF doing? Some additional dtrace access in ddb? I
didn't had it before but the dtrace probes I had in KLDs worked without
problems when running dtrace probes from userland.

Bye,
Alexander.