For what (little) it may be worth, I have noticed ... especially in the 64-bit worlds ... that memory region sizes, as reported by tools like these, can be a lot bigger until some amount of actual memory pressure is exerted that, so to speak, “compels the system to clean house a little bit.”   It seems to go straight for big allocations.   (And, this strategy seems to work just fine.)   I haven’t delved into the guts of Linux to know what might be influencing the designers’ decisions in the case of 64-bit, nor do I intend to, but the algorithms are obviously different.   (Maybe it’s partly affected by the simple fact that “chips are cheap” now?)   Of course, operating systems are always (well-) designed to be lazy, because the tradeoff is always “space vs. time.”