FWIW, even with the suggested command line switches, ArmoryDB still uses 100% of the system RAM within 60 seconds.
1) Please don't hijack somebody else's thread, create your own and post your log files.
2) There is a difference between allocated memory (malloc) and mapped files (mmap). The usage figures show you total RAM load, but the distinction is significant: allocated memory belongs to the process while mapped files boils down to hinting the OS that you want these files cached in RAM for faster access. Mapped memory does not prevent new allocations, it simply uses otherwise free resources to speed up I/O.
You are better off documenting yourself on these topics than just jumping to conclusion. Armory has been using this model for nearly 3 years now.
3) This is an open source project, feel free to submit code if you have a better solution, or at least participate to the testing phases and provide constructive feedback and bug tracking.