Copy large file cause system hangs up on ubuntu

1. Edit /etc/sysctl.conf

2. Added

    vm.dirty_background_ratio = 2

    vm.dirty_ratio = 4

    vm.dirty_bytes = 15000000

3. # sudo sysctl -p 

It seems OK on my Ubuntu 20.04.4, 62GB RAM, AMD Ryzen 7 3700 8-core