Re: [lttng-dev] Can't trace function calls

[Ramesh Errabolu via lttng-dev <lttng-dev@lists.lttng.org>]

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Thanks for the quick response, appreciate it.

At a high level this is what I did.

   1. reboot
   2. login as sudo
   3. set LD_LIBRARY_PATH to point to right locations
   4. ldd of executable to show right library versions are picked up
   5. execute the workload by specifiy LD_PRELOAD env variable
   6. expect to see a trace file in my $HOME/ltt* directory

When I say *FAIL*, I mean that there was no trace file in my home directory
~/lttng*

I read - https://lttng.org/man/3/lttng-ust-cyg-profile/v2.12/
I didn't read - https://lttng.org/docs/v2.12/#doc-liblttng-ust-cyg-profile

I have not run any lttng commands besides what I already gave. If they are
needed, I don't know what they are.

I tried experimenting with lttng commands create and list. The command to
list "traceable" points returned an error as included below.

root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin# ls ~/ | grep -i ltt
root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin# lttng create
my-kernel-session --output=~/my-kernel-trace
Session my-kernel-session created.
Traces will be output to
/home/user1/git/compute/out/ubuntu-18.04/18.04/bin/~/my-kernel-trace
root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin# *lttng list
--kerne*l
*Error: Unable to list kernel events: Kernel tracer not available*
root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin#


A grep for lttng related processes shows me a daemon service running.

root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin# ps -ef | grep ltt
root      1002     1  0 12:16 ?        00:00:00 /usr/bin/lttng-sessiond
root      1054  1002  0 12:16 ?        00:00:00 */usr/bin/lttng-sessiond*
root      3145  2861  0 12:51 pts/0    00:00:00 grep --color=auto ltt
root@RocrLnx23:~/git/compute/out/ubuntu-18.04/18.04/bin#


Regards,
Ramesh


On Wed, Mar 31, 2021 at 12:42 PM Jonathan Rajotte-Julien <
jonathan.rajotte-julien@efficios.com> wrote:

> Hi,
>
> On Wed, Mar 31, 2021 at 10:51:03AM -0500, Ramesh Errabolu via lttng-dev
> wrote:
> > I am trying to capture the list of functions being called by an app. The
> > app relies on a couple of shared libraries (libhsa-runtime64.so and
> > libhsakmt.so).
>
> ok.
>
> >
> > My experiments all *FAIL *i.e. there are no log files of the output.
>
> Not sure what you mean here. But let's continue first.
>
> > The
> > link on lttng-ust-cyg-profile does not tell me where I can get them.
>
> Could you share the "link" in question?
>
> > Instrument the build files for the two libraries to allow function
> tracing
> > by the gcc/clang flags -finstrument-functions and run workload as follows
> >
> >    - Instrument the build files for the two libraries to allow function
> >    tracing by the gcc/clang flags *-finstrument-functions* and run
> workload
> >    as follows
>
> Okai. I expect that you have read this:
> https://lttng.org/docs/v2.12/#doc-liblttng-ust-cyg-profile
>
> and this
> https://lttng.org/man/3/lttng-ust-cyg-profile/v2.12/
>
> > I am using LTTng version Ubuntu: LTTng Stable 2.12 PPA
> >
> >    - apt-get install lttng-tools
> >    - apt-get install lttng-modules-dkms
> >    - apt-get install liblttng-ust-dev
> >
>
> Looks good.
>
> > I noticed no kernel modules with substring "ltt" in it.
>
> Okai so this is where we need much more information.
>
> First of all, what are the lttng commands used for your experiments?
> (lttng create, lttng enable-channel, lttng enable-event...)
> Please provide a sample script of your experiments.
>
> Second, you are mostly performing userspace tracing here, lttng-modules (
> the
> kernel tracer) might not even be needed here unless you also want to do
> kernel
> tracing.
>
> What do you mean by "there are no log files of the output."? LTTng produces
> traces encoded in CTF (Common Trace Format) that must be read by a reader
> (Babeltrace most of the time).
>
> Cheers
>
> --
> Jonathan Rajotte-Julien
> EfficiOS
>

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