Controller memory warnings

[ipilcher]

I'm consistently seeing warnings about the amount of available memory on the controllers (masters), for example:

System memory usage of 1.266G on Node (N) ocp4-master1.aio.example.com exceeds 95% of the reservation.

The warning goes away when I increase the VM memory to 20G, so it seems like the reserved memory amount is auto-calculated from the node's total memory (but I can find no documentation of the calculation anywhere). Should the memory of the masters be bumped up to 20G?