Running the d2x-xl game, either one compiled from source or a binary version.
When in menus, the heap size (as displayed by cat /proc/pid-of-the-game/smaps)
grows with speed ranging from half megabyte to more than 20 megabytes per second.
Building a d2x-gl binary with debug enabled, the problem has been located to a
call to glGenTextures. The problem happens not every but almost every time this
function is called in the menus.
I'm not experienced enough to see if the game misuses the call. Also, I have
some reasons to assume the problem is limited to the mga driver. It happens
with a G400 MAX card, and a 16MB Millennium G200 card. It happens with Gentoo's
unofficial monolithic Xorg 6.9.0 and Gentoo's modular Xorg 7.0.0-r1
GenTextures happens in the GL driver, not the X driver.