[vbox-dev] Network adapters speed - possible bug, need insight

Ivo Smits Ivo at UFO-Net.nl
Fri Apr 26 06:32:19 PDT 2013


Hello Max,

There was apparently a bug in the VirtIO code, which has just been fixed 
in VirtualBox 4.2.12 (according to the changelog, 
https://www.virtualbox.org/wiki/Changelog). I recently discovered my 
VirtIO network interfaces were slow as well, probably because of the 
same bug. Still running VirtualBox 4.2.8, it was solved by disabling 
"TCP Segmentation Offloading" in the guest OS as suggested in the bug 
report at https://www.virtualbox.org/ticket/9380.

Ivo

Op 26-4-2013 1:01, Maxime Dor schreef:
> Hello people,
>
> For a while now, I have been facing some odd network speed issues with 
> Virtualbox but wasn't able to pint-point it down... until now !
> Please bare with me while I explain this.
>
> To give you some background story, the first time I met this issue was 
> while testing the speed of a proftpd server running in a Debian Wheezy 
> VM on a Linux Wheezy host, both 64 bits.
> Following the good recommendations of the User Manual aswell as the 
> forum folks, I decided to set the NIC to VirtIO. I was also doing this 
> speed test via an OpenVPN connection.
> The speed was always stuck at 8 Mbps for some odd reason. A bit out of 
> time, I discarded this as the VPN's fault, without further investigation.
>
> Some months later, I was installing some software (Sage BOB50) in a 
> Win 7 64 bits VM which requires access to a Sybase DB, running in a 
> Win2k8 R2 64 bits VM.
> And disaster happened : for some reason, the software was just 
> terribly slow and took minutes to open, where between physical 
> machines, it took seconds.
> I was initialy stuck with this issue, searching in the guest OS & in 
> the software configuration for some answers. After some check, I 
> noticed that the speed was of 8 Mbps (oh oh).
> At that point, I decided to change the adapter types and when both VMs 
> had the Intel 1000T desktop, it was a revelation. The program now 
> opened in seconds !
>
> I have finally been around to do some proper speed tests, and they 
> might not be concluant as such and I will let you, devs especially, 
> decide.
> To perform the tests, I have setup 2 Win7 64 bits VMs with 3 adapters 
> each.
> Virtualbox version is 4.2.8, on Debian Wheezy with Testing repos.
>
> Each VM adapater was only left with IPv4 enabled, everything disabled. 
> Static IP were used & NetBios disabled, no other config was changed.
>
> VM 1 has the following :
> NIC 1:           MAC: 080027DE6FE9, Attachment: Internal Network 
> 'virtio2virtio', Cable connected: on, Trace: off (file: none), Type: 
> virtio, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
> NIC 2:           MAC: 0800274EBA58, Attachment: Internal Network 
> 'virtio2intel', Cable connected: on, Trace: off (file: none), Type: 
> virtio, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
> NIC 3:           MAC: 080027C92821, Attachment: Internal Network 
> 'intel2intel', Cable connected: on, Trace: off (file: none), Type: 
> 82540EM, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
>
> VM 2 has the following :
> NIC 1:           MAC: 08002780E65C, Attachment: Internal Network 
> 'virtio2virtio', Cable connected: on, Trace: off (file: none), Type: 
> virtio, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
> NIC 2:           MAC: 080027009399, Attachment: Internal Network 
> 'virtio2intel', Cable connected: on, Trace: off (file: none), Type: 
> 82540EM, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
> NIC 3:           MAC: 080027592203, Attachment: Internal Network 
> 'intel2intel', Cable connected: on, Trace: off (file: none), Type: 
> 82540EM, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: 
> deny, Bandwidth group: none
>
> The idea is to have 3 networks :
> - the first with each VM with VirtIO
> - the 2nd with only one VirtIO and the 82540EM
> - the last with only 82540EM.
>
> Following IPs were given :
> virtio2virtio - 10.0.0.1/24 <http://10.0.0.1/24> - 10.0.0.2/24 
> <http://10.0.0.2/24>
> virtio2intel - 10.0.1.1/24 <http://10.0.1.1/24> - 10.0.1.2/24 
> <http://10.0.1.2/24>
> intel2intel - 10.0.2.1/24 <http://10.0.2.1/24> - 10.0.2.2/24 
> <http://10.0.2.2/24>
>
> Finally, I've run iperf 3 times with 3 different TCP window (2000, 
> 20000, 200000). I have put the results on pastebin to avoid a huge 
> spam : http://pastebin.com/niPzc1ep
>
> To sum it up :
> - virtio2virtio is capped at 8 Mbps average for a TCP window of 2000, 
> same speed as I saw in my 2 speed issues, has acceptable speed at 
> 20000 but slows down at 2000000.
> - virtio2intel gets faster & faster as the window increase but is 
> still quite slow from what we could expect (244 Mbps @ 200000)
> - intel2intel is the fastest, I get 875 Mbps @ 20000 and 1,3 Gbps @ 
> 200000 !
>
> Am I missing something obvious here? Is it a bug? From the User 
> Manual, VirtIO should be fastest, but clearly is not and can cause issues.
> I haven't had time to perform this under a Linux guest but from my 
> experience, the issue is the same.
> Please let me know if you need more info on my setup.
>
> Best regards,
> Max
>
>
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