So I had some problems with Eclipse moving crappy slow, and on top of that, I lost my auto-complete abilities for my project. The problem? I was working with a rather large PHP project and it appears that java heap size was the problem.
Solution: Increase the Java heap size used by the VM that runs eclipse like so:
./eclipse -vmargs -Xmx512M -XX:MaxPermSize=128M
And that’s it! By default eclipse uses 256MB heap size which, for my project, seemed to be too small.. but this fixed it. Now eclipse auto-complete works, and it runs smoooth as butta. 
Hope it helps others that are having problems with large projects in eclipse.