Let me rant for a bit because I've dealt with the following: Another downside is you'll get people complaining about memory usage despite mmap only paging in wh

Let me rant for a bit because I've dealt with the following: Another downside is you'll get people complaining about memory usage despite mmap only paging in what's needed. It's frustrating but users don't understand how to read memory usage at all. There's even guides out there quite wrongly telling users to look at virtual memory usage for each app. Mmap is a brilliant way to have the os handle which parts of the file actually reside in memory but you'll seriously have to deal with users that know only enough to be dangerous complaining that your app uses gb of ram when it's merely mapping a file into virtual address space to allow the os to page as it sees fit. In fact I wouldn't at all be surprised if the memory measurements in this thread were judging virtual allocation rather than physical memory used.