I don't claim to know a great deal about how it works because I haven't taken the time to walk through the code (although I did a cursory look-over of the code) but ezQuake 1.9.2 added "DarkPlaces memory manager".
I don't know if the feature is active in ezQuake 1.9.2 or if the binaries were compiled without it, but when I compared the ezQuake 1.8.3 source with the ezQuake 1.9.2 source, the changes to implement this feature are very easy.
My understanding of how the DarkPlaces memory manager works is that it allocates memory as needed, eliminating entirely the need for -mem xx or -heapsize xxxxx in the command line.
I have gamedir switching, video mode switching in the menu and I'd really like the kill any need for adding a memory command line parameter.
Anyway ... since maybe about 18 months ago, ezQuake's code has becoming outstanding from the perspective of "quality control" and I really enjoy checking in on the changes they've made. DarkPlaces has morphed too far from the original source for me to easily follow the highly evolved code, although soon I'm going to start looking harder at more DarkPlaces enhancements.
Anyway, in the ezQuake 1.9.2 source code, just search for #ifdef WITH_DP_MEM and #ifndef WITH_DP_MEM and you can see the changes. If I recall, there are only 7 changes to the code to implement this.
Source code link:
http://sourceforge.net/project/showfile ... _id=130270
Add: Although this is in the source, it does not appear to be an active feature in the binaries. I don't know whether this is because it hasn't been tested enough, still in testing or if it doesn't work right.