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

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

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

Sysprof - System-wide Performance Profiler for Linux

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