Is anyone here know, how much RAM needed for BIRD to receive all full routes Internet table?

My bird consumes around 20G of RAM for just 1 full routes 800k

                      total        used        free      shared  buff/cache   available
Mem:            31G         20G        9.4G        1.2M        1.6G         27G

Is this as expected ? or we can fine-tuning Bird ?