Debugging & Profiling

Things can go wrong, these tools may help you find the cause. If you know any more tricks please share them.

GObject Instance Count Leak Check

Requires a development (only available in debug mode) version of glib. Jhbuild recommended.

jhbuild shell
GOBJECT_DEBUG=instance-count GTK_DEBUG=interactive ./quodlibet.py

In the GTK Inspector switch to the “Statistics” tab
Sort by “Cumulative” and do the action which you suspect does leak or where you want to make sure it doesn’t repeatedly. Like for example opening and closing a window or switching between media files to present.
If something in the “Cumulative” column steadily increases there probably is a leak.

cProfile Performance Profiling

https://docs.python.org/2/library/profile.html
bundled with python

python -m cProfile -s [sort_order] quodlibet.py > cprof.txt

where sort_order can one of the following: calls, cumulative, file, line, module, name, nfl, pcalls, stdname, time

Example output:

         885311 function calls (866204 primitive calls) in 12.110 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.002    0.002   12.112   12.112 quodlibet.py:11(<module>)
        1    0.007    0.007   12.026   12.026 quodlibet.py:25(main)
19392/13067    0.151    0.000    4.342    0.000 __init__.py:639(__get__)
        1    0.003    0.003    4.232    4.232 quodlibetwindow.py:121(__init__)
        1    0.000    0.000    4.029    4.029 quodlibetwindow.py:549(select_browser)
        1    0.002    0.002    4.022    4.022 albums.py:346(__init__)
        ...
        ...

SnakeViz - cProfile Based Visualization

https://jiffyclub.github.io/snakeviz/
pip install snakeviz

python -m cProfile -o prof.out quodlibet.py
snakeviz prof.out

Sysprof - System-wide Performance Profiler for Linux

http://sysprof.com/

sysprof-cli -c "python quodlibet/quodlibet.py"
sysprof capture.syscap

GDB

gdb --args python quodlibet/quodlibet.py
# type "run" and hit enter

Debugging Wayland Issues

mutter --nested --wayland
# start your app, it should show up in the nested mutter

weston
# start your app, it should show up in the nested weston

Debugging HiDPI Issue

GDK_SCALE=2 ./quodlibet/quodlibet.py

MUTTER_DEBUG_NUM_DUMMY_MONITORS=2 MUTTER_DEBUG_DUMMY_MONITOR_SCALES=1,2 mutter --nested --wayland
# start your app, it should show up in the nested mutter