Why does swapon invokes oom-killer when enabling large chunk of swap area?

Issue

• Why does swapon invokes oom-killer when enabling large chunk of swap area?

kernel: swapon invoked oom-killer: gfp_mask=0x80d0, order=0, oom_score_adj=0

• Swapon throws error couldn't allocate enough memory for swap_cgroup.

kernel: couldn't allocate enough memory for swap_cgroup.
kernel: swap_cgroup can be disabled by swapaccount=0 boot option

• Swapon command fails when enabilng 6TiB of swap on a server with 4G of RAM as part of testing.