huge memory leak

I was playing on a redstone ready flat world when I noticed that the game randomly started to freeze.
Renderdistance: 32 chunks.
The F3 menu is showing a usage of 80 to 100% of memory use (out of 8Gb allocated).
Every time the game reaches 100% it freezes for a short time and starts again at 80% memory usage.
Dropping the view distance down to 16 chunks avoids the freeze, but the game is still running around 70 to 90 % of memory use.