[lttng-dev] [lttng-ust] Missing events when just before a process exits

[Mathieu Desnoyers]

----- On Mar 13, 2018, at 6:48 AM, THEUNISSEN Rolf rolf.theunissen at altran.com wrote:

> Hi,
> 
> I am currently tracing many processes with LTTng-UST on a system under heavy
> load, with 2 CPUs.
> 
> The traces seem to be missing ust-events near the end of a trace. After doing
> some analysis, it seems that events are missing from the other CPU then the
> process exits on. More concretely:
> 
> During the lifetime of a process:
> - Process X executes on CPU 0,1: all events are in the trace
> Just before the process is about to exit:
> - Process X executes on CPU 0: missing events from the trace
> A few mili-seconds later:
> - Process X executes on CPU1 and exits: The last events are in the trace
> 
> Is this behavior expected, or am I running into an LTTng-UST bug? And would
> there be any workaround?

Can you provide more information about the tracing configuration you are using ?
How is the session created ?

Which versions of lttng-{tools,ust} and babeltrace do you use ? Are there any
discarded events in the trace reported by babeltrace ?

If you could provide the resulting trace, it would also be helpful.

Thanks,

Mathieu


> 
> Kind regards,
> Rolf Theunissen
> 
> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com