2.3 KiB
Debugging COSMIC
An assortment of useful tools and settings for debugging COSMIC.
Logs
Cosmic-comp, cosmic-panel, and other components log to stderr, as well as journald (if present).
Wayland and X11 Protocols
Run clients with WAYLAND_DEBUG=1 to see what wayland calls are made. xtrace -n <command> can be used to see what X calls an X11 client is making.
XWayland
A tool like xprop can be used to determine if an application is running in XWayland. If xprop is unable to select a window, it is a native Wayland window.
Performance
sudo perf top can be used to see what functions, across all processes, are using the most CPU time. The -p argument can be used to restrict this to a single process. The output is more useful for executables with debug symbols.
cosmic-comp integrates Tracy for profiling. It can be built with cargo build --features profile-with-tracy --profile fastdebug, then the Tracy client can connect from the same system or a different one
Graphics drivers
eglinfo and vulkaninfo indicate what graphics cards and drivers are in use for hardware-accelerated rendering.
On systems with NVIDIA graphics, nvidia-smi has information about the GPU and driver.
DRM
The Linux DRM subsystem handles graphics cards and display controllers.
drm_info prints information about the outputs, planes, etc. associated with each GPU and their properties. The output of this command can be useful for understanding display related issues.
https://gitlab.freedesktop.org/wlroots/wlroots/-/wikis/DRM-Debugging documents how to configure DRM to enable additional logging, which can be useful for understanding some DRM driver issues.
Frozen desktop
If the desktop is frozen and ctrl+alt+f* don't work to change to a TTY, the magic SysRq key with r can be used to switch input into raw mode, so the kernel will handle the tty switch key binding. /etc/sysctl.conf or /etc/sysctl.d may need to be edited first to set kernel.sysrq=1 or another value that allows this command.
It is also possible to connect over ssh from another computer.
Then pidof cosmic-comp can be used to get the PID of the compositor. Then it is possible to investigate further with tools like gdb, using sudo gdb and then attach <pid>.