> The proportional-share fields (Pss and Pss_Dirty) in /proc/PID/smaps become less precise […] He does not think that anybody will care about these cases

That's strange to hear, because PSS is the standard way to measure actual memory taken by apps. It is more correct than RSS (because summing up PSS of different apps gets you the total memory used, which isn't the case with RSS) and I've been recommending it and using myself for ages.