Transfer speed problem with openvpn, how to fix?

Question

FreeBSD

Good afternoon.
There is a dedicated server with freebsd, openvpn is installed on it. The windows client connects to it.
the server has a 1GB/s
channel the user has a 100Mbit/s channel

Server config

verb 5
dev-type tun
dev-node /dev/tun3
daemon
keepalive 10 60
ping-timer-rem
persist-tun
persist-key
proto udp
cipher AES-256-CBC
auth SHA256
local
ifconfig 10.0.0.1 10.0.0.2
lport 
route 192.168.0.0 255.255.255.0
secret /var/etc/openvpn/server3.secret 
tun-mtu 1500
mssfix

Client config

dev tun
proto udp
cipher AES-256-CBC
auth SHA256
remote
ifconfig 10.0.0.2 10.0.0.1
route 10.1.1.0 255.255.255.0
secret client3.key
tun-mtu 1500

Speed ​​measurement with iperf-ohm
average speed without vpn - 98.5 Mbit/s
average speed with vpn - 11.1 Mbit/s
The server and client channel is not loaded, the processor too.
Changing the encryption algorithm does nothing (does not affect the transmission speed in any way).
The question is, what can cut the speed so much?

Answer 1

https://community.openvpn.net/openvpn/wiki/Gigabit...

Answer 2

First try to move away from udp towards tcp

Answer 3

The problem is in the buffers most likely.
sndbuf 0
rcvbuf 0
for both client and server.
Read https://habrahabr.ru/post/246953/
as an option
sndbuf 524288
rcvbuf 524288
push "sndbuf 524288"
push "rcvbuf 524288"
UPD. Although for BSD it may be necessary to twist somewhere else, that one is not an adviser>