No ram left

Put the summary of the bug you're having here
Loggin in and out of some of my singleplayer worlds, after the 3th, my ram = 100%

What I expected to happen was...:
That my ram will reset after loading/unloading worlds

What actually happened was...:
Ram = 100%, even with 8GB for ram...

Steps to Reproduce:
1. Log in singleplayer
2. load chunks around
3. log out
4. log in new world
== ram is full