If you’re running Linux in virtual machine environments, please be aware that the old 2GB memory requirement is now too little for best operation of the IDE. It is a very good idea to update your VMs to a minimum of 3GB. Or if you know how to install and use the PAE kernels, 4GB is even better.
I was running into all sorts of IDE sluggishness on my existing VMs after installing 2015r4 while the same IDE was running g fine on my real system (all with 8GB). I updated the VMs to 4GB and things are back to normal while running the IDE on Linux VMs.