Super slow upload on Linux KVM, but fast in Windows KVM.

[tehsu]

I have a dedicated server running proxmox 2.3, I have tested every type of setup possible on the linux kvm, using virtio, and the e1000, tested with sata and virtio also, so far I have no clue what the issue is, even the Proxmox host gets the same slow upload..

So I did some iperf testing and here are the results.

Windows to my home server.
[ 4] 0.0-10.1 sec 88.2 MBytes 73.4 Mbits/sec

Linux KVM to my home server.
[ 5] 0.0-11.2 sec 11.4 MBytes 8.55 Mbits/sec

and finally
Proxmox host to my home server.
[ 6] 0.0-11.6 sec 15.4 MBytes 11.2 Mbits/sec

I run speedtests, linux cli and windows through browser, linux gets 400Mbit down, max 60mbit up, and windows I'll see 400mbit down 400mbit up.

I thought maybe it was routing before I tested my windows KVM, but that would make no sense.

I can't come up with any conclusion as to why it is only caused on linux, I even tested ArchLinux and have been having the same issue.

--Speedtest from Windows KVM
http://www.speedtest.net/result/2706766418.png

--Speedtest from Host
Testing download speed........................................
Download: 343.83 Mbit/s
Testing upload speed..................................................
Upload: 51.96 Mbit/s