DD-WRT / OpenVPN - Speeds

[usulsuspct 1]

Okay...so I know this is a topic that comes up regularly but I feel like I am having some performance issues with my setup and was hoping someone could sanity check / offer suggestions.

 

Current setup:

 

ISP: TimeWarner Cable 30 Mbps / 5 Mbps

Modem: ASUS RT-AC56U

OS: DD-WRT v24-sp2 (04/22/14) std - build 23940

 

I am connecting to airvpn via openvpn client on the router.  Seemingly no matter what combination of servers / settings I try I end up with speeds between 8 Mbps - 12 Mbps.  I have tested with both well seeded torrents as well as various large files.  All of the tests were done while the home network was otherwise quiet (no other users using the internet).

 

While I understand that the CPU horsepower in my router is not enough to expect blazing encryption performance I had hoped for better than 12 Mbps with dual core 800Mhz.  Ancillary research on this router seems to point to others getting much better Openvpn performance than I.  If I look at the router while I am doing my tests the CPU usage of the openvpn daemon rarely passes 25% with the overall CPU usage of the router never passing 30%.

 

Here is a dump of my openvpn.conf:

 

root@dd-wrt:~# cat /tmp/openvpncl/openvpn.conf 

ca /tmp/openvpncl/ca.crt

cert /tmp/openvpncl/client.crt

key /tmp/openvpncl/client.key

management 127.0.0.1 16

management-log-cache 100

verb 3

mute 3

syslog

writepid /var/run/openvpncl.pid

client

resolv-retry infinite

nobind

persist-key

persist-tun

script-security 2

dev tun1

proto udp

cipher aes-256-cbc

auth sha1

remote 199.19.94.132 443

comp-lzo adaptive

redirect-private def1

route-noexec

tls-client

tun-mtu 1500

mtu-disc yes

ns-cert-type server

fast-io

tun-ipv6

tls-auth /tmp/openvpncl/ta.key 1

passtos

 

I have been considering upgrading my router hardware to something with more power hoping that I could squeeze a bit more out of the VPN, but I dont want to spend the money if something else is possibly holding me back.

 

Thoughts?  Suggestions?

 

 

[usulsuspct 1]

One thought I had was, is Openvpn multi-threaded?  If it were single threaded then I could see the processor on my router possibly being a bottleneck....

[Staff 10019]

One thought I had was, is Openvpn multi-threaded?

 

Hello!

 

Unfortunately not, this is an important limitation of current OpenVPN software. Hopefully it will be resolved in version 3 (the next paramount release).

 

Kind regards

[usulsuspct 1]

Hrm - I ran a wget on a large file from two hosts on my network both direct and via vpn.  Did confirm that I was able to get 3 MBps direct and only 1.2 MBps through the vpn.

 

I ran top on my router during the tests, during the VPN copy I saw the following usage:

 

em: 53140K used, 202880K free, 0K shrd, 4584K buff, 12940K cached

 

CPU0:  3.1% usr  4.7% sys  0.0% nic 74.0% idle  0.0% io  0.0% irq 18.0% sirq

CPU1: 14.6% usr 16.4% sys  0.0% nic 53.9% idle  0.0% io  0.0% irq 14.8% sirq

 

Load average: 0.61 0.32 0.26 2/50 12991

  PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND

27053     1 root     R     3088  1.2   1 24.3 openvpn --config /tmp/openvpncl/openvpn.conf --route-up /tmp/openvpncl/route-up.sh --down-pre /tmp/openvpncl/route-down.sh --daemon

 

I still feel like there is CPU power still there...