If there are performance issues with Kicad and the schematics editor running on a ATI Radeon GPU hardware consider to add a xorg option in the file
/usr/share/X11/xorg.conf.d/20-radeon.conf:
Section "Device" Identifier "Radeon" Driver "radeon" Option "AccelMethod" "exa" Option "MigrationHeuristic" "greedy" Option "EXAPixmaps" "false" EndSection
The option EXAPixmaps is documented here: https://www.x.org/archive/X11R7.6/doc/man/man4/radeon.4.xhtml