Poor OpenVPN performance (20Mbps, x84_64 with AES-NI)

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello,

I'm running OpenWRT OpenWrt 19.07.0 on top of KVM with a x86_64 server. OpenWRT sees the real CPU and AES instructions are available. The CPU is a XEON. However, with only one client, I can't get more than 2MB/s. OpenVPN server CPU is 100%. I guess AES instructions are not used.

I already read https://openwrt.org/docs/techref/hardware/cryptographic.hardware.accelerators and did try to build modules but it didn't help. I understood later hardware acceleration is already available so I don't understand this poor speed.

I don't have /dev/crypto so I guess it's my issue.

How to improve speed ?

Thanks

config openvpn 'server'
	option port '1194'
	option proto 'udp'
	option dev 'tun0'
	option dh '/etc/easy-rsa/pki/dh.pem'
	option ca '/etc/easy-rsa/pki/ca.crt'
	option key '/etc/easy-rsa/pki/private/server.key'
	option keepalive '10 60'
	option cert '/etc/easy-rsa/pki/issued/server.crt'
	option compress 'lz4-v2'
	option verb '11'
	option enabled '1'
	option client_to_client '1'
	option tls_crypt '/etc/easy-rsa/pki/tc.pem'
	option ifconfig_pool_persist '/tmp/ipp.txt'
	option persist_key '1'
	option persist_tun '1'
	option topology 'subnet'
	option server '10.5.5.0 255.255.255.0'
	list push 'dhcp-option DNS 10.5.5.1'
	list push 'dhcp-option DOMAIN example.lan'
	list push 'route 192.168.5.0 255.255.255.0'
	list push 'topology subnet'
2

OpenSSL version of OpenWRT is old and i don't think that they're using AES-NI instructions.
Version is 1.0.2, while actual is 1.1.1...