[ltt-dev] Bug in LTTv statistics ?

[Mathieu Desnoyers]

* Mathieu Desnoyers (compudj at krystal.dyndns.org) wrote:
> * Copelnug (copelnug at gmail.com) wrote:
> > There seems to be a bug in the LTTv statistics.
> > 
> > The problems is visible in the function "every_event" of the lttv/stats.c
> > file. That function is called for each event and receive a
> > "LttvTracefileStats" structure as parameter.
> > 
> > So if you check the value of the pointer to the "LttvTracefileStats"
> > received, you can see it changing between 15 and 20 value depending of the
> > trace loaded. This seems to be intended to me because each type of events is
> > associated with one and only one "LttvTracefileStats" (but a structure can
> > have many events type).
> > 
> > The bug seems to be a side effect : The structure passed to the function
> > contain the current path to the "current_event_types_tree" that is used to
> > increase the numbers of event for the event type. Or, this value is not
> > conserved between two "LttvTracefileStats" which means that the change of
> > process or state only affect one "LttvTracefileStats" and let the others to
> > their value. That means that some types of event are never affected by a
> > change of mode or process.
> > 
> > What this cause is :
> > - Many event in process 0 and Unknown mode.
> > - Difference between the total for a process of the event list in the
> > textdump and the value for the process in the statistics of the same
> > textdump.
> > 
> > Is it really a problem or am I misunderstanding something ?
> 
> Ack, I'm currently digging in the stats code to try to fix the problem.
> Thanks for the precise bug report.

OK, very light testing seems to show that the fix I just did helps a
lot. Can you try the lttv version at the head of the git repo ?

git clone git://lttng.org/lttv.git

Then make sure you got my latest commit:

cd lttv
git show 516a8712d079429962523e033e28f68704bc770a

Please follow the quickstart guide for installation, in summary:

./autogen.sh --prefix=path_to_install CFLAGS=-g
make
make install

I'll wait for your feedback before pushing a new release.

Thanks,

Mathieu

> 
> Mathieu
> 
> > 
> > Note : I use LTTv version 0.12.31 with trace version 2.5 and 2.6.
> 
> > _______________________________________________
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> > ltt-dev at lists.casi.polymtl.ca
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> 
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com