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Re: [tracecompass-dev] lttng-ust custom latency views?

Hi Martin,

On Wed, Jul 11, 2018 at 03:37:49PM +0200, Martin Oberhuber wrote:
> Hello TraceCompass experts,
> 
> I have instrumented my embedded application with lttng-ust, adding 4
> tracepoints without arguments (a1, a2, a3, a4). My app is running on a
> Linux 3.14.70 ARM board, and I'm using lttng 2.6.0 "Gaia". I'm uploading
> the data to an Ubuntu host. On the host, I can run babeltrace to get the
> raw tracing data.
> 
> Now I'd like to get some statistics about the time my app takes between
> a1->a2, a2->a3, etc. I'd like to see the min/max, navigate to the min/max,
> graph latency over time and see a histogram of latency distribution.
> Similar to the System Call Latency Views in Trace Compass.
> 
> I was hoping that I could write such an analysis in Python, deriving from
> the lttng-analyses. So I've tried that on a Kernel trace on my ARM board
> first (lttng-analyses-record , version v0.6.1). But uploading the Kernel
> trace to the host and running a simple command like "lttng-cputop-mi
> mytrace" just thinks a while and then prints
> {"error-message": "Error: Cannot run analysis: 'State' object has no
> attribute 'tracer_version'"}
> 
> My questions:
> 
>    - Is it a reasonable approach writing an external analysis for my
>    lttng-ust in Python? Or is there any simpler / better way getting the
>    latency statistics that I want?

Using python is quite reasonable with the babeltrace bindings. You can also use
the TraceCompass Data Driven Analysis [1]. Not sure if your use case is
completely covered, people from TraceCompass mighthave more information
regarding this.

[1] http://archive.eclipse.org/tracecompass/doc/stable/org.eclipse.tracecompass.doc.user/Data-driven-analysis.html

>    - Any clue what I could do to get lttng-analyses to work in my
>    environment?

Was there any other error message?

What is the complete command used for lttng-analyses?

Could you share the trace/metadata?

>    - How could I move on getting the latency statistics?
> 
> Thanks a lot for any hints!
> Martin

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-- 
Jonathan Rajotte-Julien
EfficiOS