I've found the set of short articles on memory here to be excellent:

http://duartes.org/gustavo/blog/post/page-cache-the-affair-b...

I love seeing links like this on HN: you can actually learn something, not just read some opinionated article :)

Worth also looking here: http://www.cs.gmu.edu/cne/pjd/PUBS/Workingsets.html

Had the great pleasure of being one of his students years ago during my undergrad. Hands down the best professor I've ever had.

http://en.wikipedia.org/wiki/Peter_J._Denning

Here are some other great resources on understanding how the OS (in this case linux) manages the memory, and how the hardware works.

http://tldp.org/LDP/tlk/mm/memory.html

http://lwn.net/Articles/250967/

Makes me wonder how fast OS level garbage collection could be, without the need to have a virtual memory layer in between...