[lttng-dev] Difference in metadata between per-PID and per-UID traces

[Mathieu Desnoyers]

* Thibault, Daniel (Daniel.Thibault at drdc-rddc.gc.ca) wrote:
>    I notice that the metadata of per-PID user-space traces has three attributes which are dropped from the equivalent per-UID trace:
> 
> Per-PID trace:
> 
> env {
> 	hostname = "sds-dut-vb";
> 	domain = "ust";
> 	tracer_name = "lttng-ust";
> 	tracer_major = 2;
> 	tracer_minor = 3;
> 	tracer_patchlevel = 0;
> 	vpid = 7024;
> 	procname = "simple";
> };
> 
> Per-UID trace:
> 
> env {
> 	hostname = "sds-dut-vb";
> 	domain = "ust";
> 	tracer_name = "lttng-ust";
> 	tracer_major = 2;
> 	tracer_minor = 3;
> };
> 
>    The trace data are the same in this case (two trace sessions capturing the same events in parallel), so this change in metadata only shows up in babeltrace's output (when using '-f all -n all' for example).
> 
>    Is this intentional?

Yes

>  It does mean per-UID traces "anonymize" the event data slightly.  And why is "tracer_patchlevel" dropped alongside the process-related attributes?

Because different processes could use different tracer versions.

Thanks,

Mathieu


> 
> Daniel U. Thibault
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com