[lttng-dev] status of lttng top

McDermott, Andrew Andrew.McDermott at windriver.com
Fri Oct 26 08:40:15 EDT 2012

Julien Desfossez <jdesfossez at efficios.com> writes:

> Hi,
>>>>> LTTngTop is still work in progress and will remain that way for a long
>>>>> time, but the version in the PPA (or in the master branch in git) is
>>>>> perfectly usable for offline traces (traces recorded and replayed
>>>>> through LTTngTop).
>>>>> The "live" branch is more experimental and requires patches in both
>>>>> Babeltrace and Lttng-tools (all documented in the README-LIVE file), but
>>>>> it worked at the time of Plumbers, I didn't have much time since then to
>>>>> rebase the branches.
>>>>> I am waiting for the release of Lttng-tools 2.1 (currently in RC) before
>>>>> merging those patches. After these patches are integrated, LTTngTop will
>>>>> be able to work live without any modifications, so directly reading
>>>>> traces in memory shared with the tracer.
>>>> Thanks for this info.
>>>> Right now my interest is with the live streaming; we have a use case
>>>> where the live streaming is really the only practical solution.
>>>> Very roughly, would you expect the RC series to conclude this year, or
>>>> (early) next year?
>>> Just to clarify, are you interested in live network trace reading or
>>> live in-memory reading ?
>>> The patches I was talking about are for in-memory trace reading.
>> So I guess I don't understand enough of the low-level detail here.  What
>> I was interested in was being able to consume events, maybe periodically
>> (1 /s), from a trace written by another process on the same machine.  I
>> guess that would fall under in-memory trace reading.
> Ok I will just describe this a little more, when we talk about live
> reading the trace, we have two aspects :
> - reading a trace while it is being written on disk (whether it is
> received from the network or from a local consumer)
> - reading a trace directly from memory mapped buffers between the tracer
> and the consumer without writing the trace files.
> So if you want to read the trace on the machine that is being traced
> without ever writing the trace on disk, yes you want the in-memory trace
> reading.
> For 2.2, the focus is to support live trace reading from disk (local and
> network).
> In my development branches (referenced in previous email), I have code
> that provides live trace reading from memory, I will try to merge it in
> 2.2 but I cannot guarantee it will be accepted since it is not the
> current priority (but definitely a use-case we want to support).
> I hope it clarifies the situation,

Yes it does.  Many thanks.


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