[ltt-dev] UST use case: Tracing QEMU/KVM

[Pierre-Marc Fournier]

Selon Stefan Hajnoczi <stefanha at gmail.com>:

> On Tue, Jun 1, 2010 at 7:45 PM, Pierre-Marc Fournier
> <pierre-marc.fournier at polymtl.ca> wrote:
> > Sure, it would be great if ust were in more linux distributions. I believe
> > what we can do for now is to spread the word (like you are doing with the
> > qemu/kvm community) and be patient.
> >
> > It might put off some people that ust is not packaged, but we need early
> > adopters who are willing to compile software themselves to put pressure on
> > the community. This appears to be a necessary phase before distributions
> > invest time and money to create and maintain packages.
> >
> > Any ideas to encourage further the distributions to package ust would be
> > welcome of course.
>
> I'm interested in how a production app should use UST.  Is the goal
> for programs to ship linked against libust?
>

I guess it depends on the specific use case.

If someone is using libust to monitor continually a process, it would probably
be better to link directly to libust.

If someone is shipping an embedded system with a particular application they
want to trace occasionally, the way to go would probably be to ship the program
linked with libust, or to start it with a script that LD_PRELOADs libust.

For Linux distributions, it is probably not desirable to have every single
program shipped already linked with libust. If they need to be traced, they can
be started with libust.so LD_PRELOADed. Alternatively, we may add at some point
the possibility to load the tracing library in a program that is already
running.

I would be interested if other have different points of view. I certainly cannot
imagine all the use cases.

pmf