Re: [Qemu-devel] [PATCH 2/3] trace: add tracetool simpletrace_stap format

[Stefan Hajnoczi]

On Tue, May 27, 2014 at 03:10:30PM +0200, Lluís Vilanova wrote:
> Stefan Hajnoczi writes:
> 
> > This new tracetool "format" generates a SystemTap .stp file that outputs
> > simpletrace binary trace data.
> 
> > In contrast to simpletrace or ftrace, SystemTap does not define its own
> > trace format.  All output from SystemTap is generated by .stp files.
> > This patch lets us generate a .stp file that outputs in the simpletrace
> > binary format.
> 
> > This makes it possible to reuse simpletrace.py to analyze traces
> > recorded using SystemTap.  The simpletrace binary format is especially
> > useful for long-running traces like flight-recorder mode where string
> > formatting can be expensive.
> 
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> >  scripts/tracetool/format/simpletrace_stap.py | 73 
> > ++++++++++++++++++++++++++++
> >  1 file changed, 73 insertions(+)
> >  create mode 100644 scripts/tracetool/format/simpletrace_stap.py
> 
> > diff --git a/scripts/tracetool/format/simpletrace_stap.py 
> > b/scripts/tracetool/format/simpletrace_stap.py
> > new file mode 100644
> > index 0000000..4e7f7e7
> > --- /dev/null
> > +++ b/scripts/tracetool/format/simpletrace_stap.py
> [...]
> 
> Should the build automatically generate a file using this format? (just for
> convenience)
> 
> Also, it might be worth mentioning this file in the "SystemTap" section of
> "docs/tracing.txt".

I'm still trying to figure out how to best distribute and integrate into
make install.  Will send a follow-up patch series to hook into the
build.

I wasn't sure whether to generate the simpletrace-stap file during build
or ask the user to customer trace-events to just the events they want to
trace.

Frank Ch. Eigler of SystemTap fame explained yesterday how to build the
simpletrace-stap file once but let the user configure a subset of
probes.  I think this is the cleanest approach and I am experimenting
with that today.

Stefan