[ltt-dev] how to use lttng in large workload with long time

[Mathieu Desnoyers]

* Li, Chanjuan (lichanjuan04 at gmail.com) wrote:
> hi,all:
>     Now I want to use lttng to analyse performance of a MPI application
> on wether forecast. The application will run about 2h. When I use lttng
> to collect events, it generates 50G results . It is hard to analyse with
> such huge data.

Is LTTV having problems with those 50GB of data ?

> So I want to reduce the events to be recorded instead of
> ltt-armall events.
> I try ltt-armtap, but it does not work because there is no /proc/ltt in
> my machine. In addtion, I read the LTTng manual, there is a flight
> record mode. I want to know that could help in such context. thanks in
> advance!

Flight recorder mode:

You can configure tracing in flight recorder mode. The trace session
will only write events into a trace buffer in memory, without saving the
trace to disk. So the oldest events will be constantly overwritten.

If you know a particular behavior or problem in your application you are
looking for (a trigger), then you can keep flight recorder tracing
active for the whole 2 hours, but only save snapshots when the situation
you are looking for happens.

Mathieu

> 
> 
> 
> 
> best regards
> 
> lily
> 
> 
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-- 
Mathieu Desnoyers
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