The OS isn't very smart about it because it quantizes everything along page boundaries and has no semantic understanding of the data. That works fine in the ty

The OS isn't very smart about it because it quantizes everything along page boundaries and has no semantic understanding of the data. That works fine in the typical desktop-system case where you have 100 processes using a few megabytes each and at any given time only one or two are active. When you're running one server process that uses all the system's memory, you can be a lot more efficient by handling it yourself.