[Ksummit-2008-discuss] DTrace

David Miller davem at davemloft.net
Mon Jun 30 13:48:44 PDT 2008


From: Arnaldo Carvalho de Melo <acme at redhat.com>
Date: Mon, 30 Jun 2008 17:22:33 -0300

> Em Mon, Jun 30, 2008 at 04:10:31PM -0400, Theodore Tso escreveu:
> > On Mon, Jun 30, 2008 at 03:25:33PM -0400, Frank Ch. Eigler wrote:
> > Stupid question --- has anyone thought about writing tools to strip
> > out specific debug information not needed by Systemtap?  For example,
> > I assume systemtap doesn't need the line number information, since you
> > can't set probes on arbitrary line numbers (and even if you could,
> > such tapsets would be so brittle that it wouldn't be funny); so would
> > the debuginfo files be smaller if that information were stripped out?
> > I understand that this would make the files less useful for
> > kdump/crash, but for systemtap only users, it might be quite useful.
> > What about stripping out the text segment of the object files, so you
> > aren't storing the information twice on disk, or compressing the
> > debuginfo files so they take up less room on disk?
> 
> Yes, its called CTF, Compressed C Type Format, in DTrace land:
> 
> http://opensolaris.org/os/project/ppc-dev/task_map/ctf/
> 
> DaveM wrote a CTF loader that I included in my dwarves package, so that
> we can pretty-print and use all the other features in pahole on files
> with CTF sections, such as the Open Solaris kernel and the userland
> binaries, that all ship with CTF embedded, dispensing the usage of
> -debuginfo packages, all AFAIK.

One thing you lose with CTF is the stack unwind tables,
and I don't know if systemtap needs that or not.

If someone can state what the absolute minimum requirement
is for systemtap to be able to analyze a binary properly,
we can figure out if CTF provides it.


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