[lttng-dev] Strange result from LTTng porting to ARM

[Thibault, Daniel]

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Date: Wed, 12 Nov 2014 23:26:41 +0800
From: J Lin <jmlin.jmlin at gmail.com>

> I've recently ported LTTng to ARM and I can't seem to understand what is going wrong with my results. I ran a typical session with "lttng enable-event -k -a" for test. Here are the observations:
>
> 1. only "lttng_xxx (e.g, lttng_statedump_interrupts)" are recorded 2. different sessions yield trace on different CPU (the system has 4) but not for all 4, just 1 cpu 3. no recorded session span more than 1 second though I would run sleep (i.e., 10s) between "start" and "stop"
>
> This leads me to believe LTTng might be dependent on something in the system that isn't present. This is a customized kernel of a client. It has all required configs.
>
> If there is a trigger mechanism after running "lttng start", what would it be? It seems it grabs items initially then doesn't continue. I read in one of the papers that LTTng is architecture dependent. Any help is appreciated.
>
> Mike

   How exactly did you "port" LTTng to ARM?  As far as I know, you need only rebuild it there.  Your symptoms lead me to believe you may have not installed the requisite lttng-modules.  Did you test user-space tracing?

Daniel U. Thibault
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