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

Hi Martin,

On the Trace Compass, as Jonathan mentioned, the XML analyses [1] might be a good starting point. The segments analyses in particular include min/max, latency and statistics analyses with some built-in views. If you decide to go this way, here's also a blog post by one Trace Compass user about his usage of the XML analyses [2].

But doing python analyses is a reasonable approach too. I'm not too sure what the error may be though. Have you tried doing the same not on an ARM board? Or with more recent version of lttng-analyses?



On 2018-07-11 09:37 AM, 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?
  • Any clue what I could do to get lttng-analyses to work in my environment?
  • How could I move on getting the latency statistics?
Thanks a lot for any hints!

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