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

[Mathieu Desnoyers]

Hi, 

There is little we can do without information about the kernel 
customization that have been done in your use-case. Most likely, 
there might be one customization that breaks tracepoints located 
in the core kernel. It appears that only the tracepoints present in 
the lttng-module modules are traced. 

Just as a guess, do you have CONFIG_JUMP_LABEL=y 
in your config ? Try setting it to "n'. Just in case they would 
happen to be broken on your specific kernel version/customization. 

Good luck! 

Mathieu 

----- Original Message -----

> From: "J Lin" <jmlin.jmlin at gmail.com>
> To: "Daniel Thibault" <Daniel.Thibault at drdc-rddc.gc.ca>
> Cc: lttng-dev at lists.lttng.org
> Sent: Thursday, November 13, 2014 6:12:14 AM
> Subject: Re: [lttng-dev] Strange result from LTTng porting to ARM

> Hello Daniel,

> I should correct myself and say cross compiled LTTng to run on ARM. We
> installed lttng-modules via insmod and verified with lsmod. Regarding
> lttng-modules, there was a problem compiling where duplicate definition
> occurred. We use kernel version 3.8 and in the source code saw the
> conflicting section "should be" guarded for version less than 3.15. So we
> added version check to work around it.

> We have not tested ust yet. But have compiled all three (lttng-ust,
> lttng-tools, lttng-modules) and placed on development board. Right now, we
> are just doing a simple trace for a certain irq that triggers every 4ms.
> This is the most information we got:
> [00:01:36.985006316] (+0.001175688) (none) lttng_statedump_interrupt: {
> cpu_id = 0 }, { irq = 29, name = "GIC", action = "twd" }

> Also noticed this when creating a session:
> [ 2][ 64.512057] ##### send signal SIG : 10, lttng-sessiond(373)->lttng(262)
> __send_signal

> Thanks,
> MIKE

> 2014-11-13 3:10 GMT+08:00 Thibault, Daniel < Daniel.Thibault at drdc-rddc.gc.ca
> > :

> > ----------------------------------------------------------------------
> 
> > 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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-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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