[piperswe]

Mapped but unused memory is imaginary (at least, on modern UNIX systems). It's not actually using any physical RAM.

[atombender]

That is true, but I don't see other applications consuming ever-increasing amounts of virtual memory, so to me it suggests a bug.

[junon]

Well, depends. Not always zero but in a good implementation not more than a few bytes per allocation, at most (if not zero).