root@s6:~# openvpn --genkey --secret /tmp/secret
root@s6:~# time openvpn --test-crypto --secret /tmp/secret --verb 0 --tun-mtu 20000 --cipher aes-128-cbc
Sun Jun 16 22:15:44 2019 disabling NCP mode (--ncp-disable) because not in P2MP client or server mode

real    0m8,213s
user    0m8,112s
sys     0m0,036s
root@s6:~# time openvpn --test-crypto --secret /tmp/secret --verb 0 --tun-mtu 20000 --cipher aes-256-cbc
Sun Jun 16 22:15:59 2019 disabling NCP mode (--ncp-disable) because not in P2MP client or server mode

real    0m8,073s
user    0m7,944s
sys     0m0,076s
root@s6:~# time openvpn --test-crypto --secret /tmp/secret --verb 0 --tun-mtu 20000 --cipher aes-128-gcm
Sun Jun 16 22:16:09 2019 disabling NCP mode (--ncp-disable) because not in P2MP client or server mode

real    0m7,220s
user    0m7,132s
sys     0m0,032s
root@s6:~# time openvpn --test-crypto --secret /tmp/secret --verb 0 --tun-mtu 20000 --cipher aes-256-gcm
Sun Jun 16 22:16:19 2019 disabling NCP mode (--ncp-disable) because not in P2MP client or server mode

real    0m7,151s
user    0m7,060s
sys     0m0,056s