After some more testing, I can confirm that the memory leak actually occurs in 'gtk2-engines-gtk-qt'. In KDE, setting 'GTK styles and fonts' to use a specific style instead of "Use my KDE style in GTK applications" makes GTK apps run smoothly and without any freezes. After several hours the 'Xorg' process uses around 40MiB, as opposed to 200MiB+ (topped at close to 2GiB!) before.
-- GTK applications leading Xorg to huge memory usage https://launchpad.net/bugs/51421 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
