[ltt-dev] Getting current process from Log files

Mathieu Desnoyers compudj at krystal.dyndns.org
Fri Apr 1 11:18:14 EDT 2011

* Radhika Chowdary (radhika.putty at gmail.com) wrote:
> Hi
> We are implementing importer for LTTng and not using any existing C parser
> or linuxtools plugins.

Why ? You might want to consider looking at libltttraceread and lttv.
These problems have already been solved, and the code is public.

> I need some info on how we get the currently running
> process. From what i see from the existing C parser code i understand its
> the sched_schedule event which can help in getting currently running
> process. We get the timestamp of when a sched change event happened and add
> the process to the stack with timestamp. So any event occuring after the
> sched_schedule event we get the process that was scheduled in as currently
> running process.

.. for the cpu sched_schedule was executed on.

> Is my understanding currect. If that is true and we get an
> event before any sched_schedule or fork events how can we get the process
> that generated the event. Would it be the init process?

Nope. See state.c in lttv. This is why we have unknown state at trace
start, ability to build the state from the events incrementally for
flight recorder mode, and "state dump" machinery to get to a point where
the state is fully known when we have a "normal/discard" trace.



> Thanks
> Radhika

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Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.

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