Something in OSX paging is broken. See http://workstuff.tumblr.com/post/20464780085/something-is-de... for details. Apple refuses to fix this for years. This rendered my old Core2Duo/2GB RAM/spinning disk MBP useless even for web browsing. This sort of system rot is one of the reasons I'm running Arch on my Haswell MBP/16GB.