Unity Editor constantly eats RAM

When im using the Editor, my RAM usage keeps getting higher. After a clean boot and Unity start i have around 4GB used RAM and no swap. Then i start using the Editor ( moving prefabs around etc) on a scene with a good amount of assets. I would expect a fairly high RAM usage - but nothing like this. Without doing anything special the RAM usage climbs up to my maximum of 8GB and then fills the rest of my SSD (Swap) until its out of memory. Then OSX pauses Unity until the RAM-compression or something else frees up some memory.

Usually this happens at 8GB (RAM) and 12GB(SWAP). It happens on each of my scenes ( just way slower on the small scenes). I have attached a screenshot while running, and immediately after i shutdown Unity.

My System is: Unity 5.3 Pro (happens on 5.1.1 as well) MacbookPro (late 2013) 8GB RAM Intel Iris Graphics 128GB SSD