WireGuard network perfomance

[Sergey <me@prok.pw>]

Hello guys.

First of all thanks for the WireGuard project: it really simple & 
powerful and no more headaches with openvpn :)

My question about network perfomance, I tested network speed with 
iperf3 and got these results:

Raw test (no WireGuard):

$ iperf3 -c PUBLIC_IP
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  98.1 MBytes  82.3 Mbits/sec   25             
sender
[  4]   0.00-10.00  sec  93.6 MBytes  78.5 Mbits/sec                  
receiver

So I got ~80 Mbits/sec

And WireGuard test:

$ iperf3 -c PRIVATE_IP
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  53.2 MBytes  44.7 Mbits/sec  1863             
sender
[  4]   0.00-10.00  sec  46.1 MBytes  38.7 Mbits/sec                  
receiver

And there is ~40 Mbits/sec, so half of original.

I missed something? Probably I need to configure something /etc?
btw what is "Retr" column in iperf? Why it so big with WireGuard?

Anyway that's good result for me, as openvpn can only give me something 
~15 Mbits/sec.

Best regards, Sergey.