[lttng-dev] lttng-track by process/thread name

[Milian Wolff]

On Thursday, March 21, 2019 6:24:28 PM CET Mathieu Desnoyers wrote:
> ----- On Mar 21, 2019, at 12:21 PM, lttng-dev lttng-dev at lists.lttng.org 
wrote:
> > Hey all,
> > 
> > I stumbled upon lttng-track which sounds quite useful when one wants to
> > concentrate on the events of a single process. But how is one supposed to
> > use this? Usually, I start lttng before I start my application - I thus
> > don't know the PID yet. Is there a trick that I'm not aware of, or can it
> > really only be used to track after starting an application?
> 
> At the moment, you need to know which PID you want to track.
> 
> I have a prototype using ptrace to do something similar to
> 
> strace --follow-children /path/to/executable
> 
> but I only had time to do the underlying plumbing. All the user interface
> needs to be designed and implemented. If you are interested to look into
> this I could dig out my prototype branch.

Hey Mathieu,

this sounds very interesting! While an experimental feature would be 
sufficient for me personally, I'm regularly advocating people to try out 
LTTng. They often ask me how to get "rid" of the noise, especially when you 
are running on your development machine where tons of unrelated applications 
are also running and producing lots of events. Having a proper solution to 
this problem upstream would be very beneficial, I think.

That said: I obviously know the value of having *everything* tracked, since 
that actually allows you to answer most complicated questions where the 
interaction between all applications on a single system, all competing for the 
same resources, paints the full picture.

Thanks

-- 
Milian Wolff | milian.wolff at kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
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