On 2025-06-02 10:37, David Aldrich via lttng-dev wrote:
Hi,
I am trying to use lttng-ust-cyg-profile.
Our application is large so, so far, I only compile main.cpp with
compiler option '-finstrument-functions' (I don't specify option
'-pg').
Our app must be run as root so I run it, and capture with lttng, like this:
lttng create app_trace
lttng enable-event --userspace 'lttng_ust_tracef:*'
lttng enable-channel --kernel --session app_trace kernel_channel
lttng enable-event --kernel --all --channel kernel_channel --session app_trace
export LD_PRELOAD=liblttng-ust-cyg-profile.so
lttng start
sudo -E ./myapp
lttng stop
I notice that many events get discarded:
Warning: 198522 events were discarded, please refer to the
documentation on channel configuration.
I then import into TraceCompass. I see the traces in the Resources
View, but when I expand Experiment > Views, all 3 'LTTng-UST
CallStack' entries are striked through so I can't select them. So I
can't visualise the function calls.
Any idea what I am doing wrong please?
AFAIK, the "LD_PRELOAD" environment variable is cleared by
sudo when running its child process for security purposes.
Thanks,
Mathieu
Best regards, David
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
