Lttng performance measurement

[ece_student]

Hi, I am trying to measure performance by adding some code.
My target firmware version is 3.4.
And, I put perf code as follows.

1. perf_alloc

• When AP_Scheduler is initialized
• _perf_XX = hal.util->perf_alloc(AP_HAL::Util::PC_ELAPSED, perfid);
• As a example of perfid, it was “1” “2” and so on

2. perf_begin

• In AP_Scheduler::run function, I put it before each task start (before “_tasks[i].function()” this code)

3. perf_end

• After each task ends (_tasks[i].function();), I put it.

However, I cannot see any results.

I followed the guildline here
http://ardupilot.org/dev/docs/using-linux-trace-toolkit-ng-lttng-to-trace-ardupilot-in-realtime.html
And I installed related libraries.

However, when I reboot the board, I could see only
pi@navio: ~$sudo lttng list --userspace
→ UST events:
None

w/o sudo it is same.

Since I am not sure about “ardupilot” in the below.
lttng enable-event --userspace ardupilot:count
lttng enable-event --userspace ardupilot:end
lttng enable-event --userspace ardupilot:begin

I changed it into “0” or “1” since I put that name when I call perf_alloc

In addition, I cannot see any results even with SCHED_DEBUG parameter setting which must show some results I believe.

Is there any person who have experience with lltng on NAVIO2?

Thank you

PS. Note that I also tried all lltng commands with sudo since ardupilot runs on root privilege. But, I couldn’t see any difference.

[george.staroselskiy]

@ece_student

Is there any person who have experience with lltng on NAVIO2?

By default ArduPilot is not linked to lttng. You can install liblltng dev packages on the Raspberry itself and build ArduPilot there. Make sure that waf configure --board=navio2 states that lttng is detected and linked to. That is the easy but slow way.

Another approach is not for faint-hearted. We’ll cross-compile ArduPilot on a Linux host against the sysroot with the g++ wrapper that’s properly symlinked like this:

arm-linux-gnueabihf-g++:

#!/bin/bash 
exec arm-linux-gnueabihf-g++.real --sysroot=$SYSROOT "$@"

SYSROOT is the environment variable to a mounted rootfs from Raspberry Pi with all the needed libraries.

So it all boils down to this:

1. Grab our image and save it to $IMAGE_FILE and extract
2. sudo kpartx -av $IMAGE_FILE to make a loopback device
3. sudo mount /dev/mapper/loopXp2 rootfs to mount it
4. systemd-nspawn -b --bind /usr/bin/qemu-arm-static -D rootfs to boot the image. Make sure binfmt module is loaded
5. Now you have an emulated with qemu Raspberry Pi where you can poke around.
6. sudo apt-get install liblttng dev packages inside the container
7. Quit the container

After this steps you’ll have a rootfs with all libraries you need
8) Point SYSROOT to rootfs directory
7) waf configure --board=navio2 on your host should now detect liblltng and link against it.

@ece_student

In addition, I cannot see any results even with SCHED_DEBUG parameter setting which must show some results I believe.

You should see a message every once in a while in your GCS after you set it.