Re: malloc probes for Systemtap

[Alexandre Oliva <aoliva at redhat dot com>]

On Oct  2, 2012, Roland McGrath <roland@hack.frob.com> wrote:

> I'm not at all an expert on malloc implementation details, which is
> what goes to what the useful set of probes to have is.

> So, you need to get someone who is expert on malloc details to review
> your choice of probe locations, names, and parameters.

Since I suppose we can't resort to Uli, who's made most changes to
malloc/ during his time as maintainer, I guess we may have to go with
our own expertise.

I guess myself and Siddhesh have been the most recent âmaintainersâ of
malloc.  I've studied it a lot myself while preparing this patch, and
Siddhesh did so even more deeply for other reasons.  Jeff Law is
somewhat familiar with malloc and he's seen this patchset and, to some
extent, guided the requirements for the probes I introduced.

Any objections to my going ahead with the probes as they are, that
internal reviews at Red Hat have IIUC already concluded would satisfy
the requirements of exposing unusually expensive malloc behavior to
probing?

> What we have in the way of
> documentation for the existing probes is just
> nptl/DESIGN-systemtap-probes.txt and elf/rtld-debugger-interface.txt.

So I noticed.  I wasn't happy with that and decided it belonged in the
manual, but...  I hadn't considered ABI stability aspects of probes.
*blush* :-)

Anyhow, it wouldn't be hard a tall to reformat the texi input into a
.txt file, or perhaps to have the newly-introduce docs unconditionally
removed from the formatted manuals.

> (There was some past discussion about this when the earlier probes
> went in, but it only resolved to the point that we achieved consensus
> that we didn't really need to resolve it right then.)

:-)

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer