Occasionally, when I go into one of my single player worlds in creative, my Minecraft studders when showing 35+ FPS. In bad cases, my Minecraft severely lags at ~6 FPS and slows to a halt. I notice that my RAM usage skyrockets to 85-95% in the F3 menu and total usage in task manager shows nearly 2G being used when it is usually only around 1G.

What I Expected To Happen:
I would normally play Minecraft with no studdering or lag.

What Accually Happened:
Occasionally, I get massive lag when I join a certain world to the point where Minecraft freezes.

I would also like to post my log after it crashed. It shows server overload and it running behind 2Kms to 4Kmsand even (unrecorded in that log) 14Kms. Here is the log: http://justpaste.it/gn99