The LLMemory method getCurrentRSS() is defined to return the "resident set
size," but in fact on Windows it returns the WorkingSetSize -- and that's
actually what callers want from it: the total memory consumed by the
application for statistics purposes. It's not really clear what users gain by
knowing how much of that is resident in real memory, versus the total
consumption. So despite the commentation and the method name itself, on Mac
make it return the virtual size consumed.