I am not seeing this problem yet in 2015.12. You need to give more info than just saying "Lightroom eats all my memory". What are you doing when this happens. I have used the new version for quite awhile and the memory usage goes up and down but is not excessive.
Example, if I sychronize folder or try remove over 100 image or try make image groups.. > Pc crashes when the memory is run out.
The problem occurred immediately after the upgrade.