[lttng-dev] events injection / merging traces

[Jonathan Rajotte-Julien]

Hi Carlo,

> 
> > This leads to, as always, whats is the end goal here?
> 
> This is the context: I'm tracing a Linux kernel (using LTTng) while in
> parallel I'm tracing a process running in a bare-metal OS (running on the
> same machine but on different cores using a partitioning hypervisor).

Nice.

> 
> The binary trace data obtained from the bare-metal OS is converted to CTF
> using babeltrace in a format resembling LTTng (to be analyzed with
> TraceCompass).

In both case, babeltrace and tracecompass based analysis should leave the trace
merging to the parser/decoder/muxer. There should be no need to merge them in a
single CTF trace.

The thing that is important is to correlate the clock from both traces to allow
the tools to do a proper merge. Then you consume the events and build state etc.
How you correlate those clocks depends on the tracing scenario.

I would recommend you speak to the Tracecompass devs [1] on how they handle multiple
"kernel" traces (linux + converted baremeta) in "experiment" [2] and how clock
correlation works [3] on their side. This is if you plan to mostly use
Tracecompass for analysis. If you plan to use babeltrace, we can discuss this
more as needed.

[1] https://www.eclipse.org/tracecompass/#community
[2] https://archive.eclipse.org/tracecompass/doc/stable/org.eclipse.tracecompass.doc.user/Trace-Compass-Main-Features.html#Creating_an_Experiment
[3] https://archive.eclipse.org/tracecompass/doc/stable/org.eclipse.tracecompass.doc.user/Time-offsetting.html#Time_offsetting

-- 
Jonathan Rajotte-Julien
EfficiOS