[lttng-dev] Trace files not getting generated

[Tommy Huynh]

Thank you for your prompt response.

Regarding your question:


The lttng client seems to be starting a new session daemon at
line 97 of t4-lttng-httperf.log. Did it crash in the meantime? Or
perhaps these executions are unrelated?
    These executions are probably unrelated. I did run the experiment 
    several times to make sure it's reproducible.



It is expected if the IO capacities of the machine are exceeded by the
event throughput. That wouldn't surprise me since you have 24 cores 

producing events with all kernel events enabled.
    Are you suggesting a scalability issue with LTTng? 
    What is the best way to address this? 


Regards,
--
Tom


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On Wednesday, October 8, 2014 4:11 PM, Jérémie Galarneau <jeremie.galarneau at efficios.com> wrote:
Good question... The consumer seems able to flush and I don't really
see any errors...
However, the lttng client seems to be starting a new session daemon at
line 97 of t4-lttng-httperf.log. Did it crash in the meantime? Or
perhaps these executions are unrelated?

As for the messages in dmesg, the dropped events are not necessarily
indicative of an issue; it is expected if the IO capacities of the
machine are exceeded by the event throughput. That wouldn't surprise
me since you have 24 cores producing events with all kernel events
enabled.

By the way, would you mind posting this on the lttng-dev mailing list?
Perhaps someone can help us figure it out faster.

Regards,
Jérémie


On Wed, Oct 8, 2014 at 4:14 PM, Tommy Huynh <tom.huynh15 at yahoo.com> wrote:
> Hi Jérémie,
>
> LTTng doesn't generate the trace files and prints something like this:
>     ring buffer relay-discard, cpu 0: records were lost. Caused by:
>       [ 5626697 buffer full, 0 nest buffer wrap-around, 0 event too big ]
> The behavior seems similar to this email thread:
> http://lists.lttng.org/pipermail/lttng-dev/2013-December/022059.html,
>
> but my log doesn't show the problem with the consumer daemon.
>
> I'm running on a Freescale T4240qds development board with Linux 3.12.19
> and LTTng 2.4.
>
> The run log is attached in this email along with the log file produced with:
>
>     lttng-sessiond -vvv --verbose-consumer > sessiond.log
>
> Could you let me know what's wrong?
>
> Regards
> --
> Tom Huynh



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com