On 27.09.2013 11:03, Patrick Herzfeld wrote:

Hi

I'm currenty testing network QoS implementations stumbled upon quite strange results when using QoS definitions inside the virtdomain xml.

I'm testing bandwidth from a virtdomain towards a hardware server connected to the same switch, both connected to gigabit ports. Iperf tells me the bandwidth is around 939 Mbit/s.

I added this to my virtdomains xml: <bandwidth> <inbound average='1280'/> <outbound average='1280'/> </bandwidth> This should limit the bandwidth to around 10 megabit/s 1280 kilobytes/s, however i get only around 5.14 Mbits/sec...

Has anyone an idea what causes this difference?

I already checked the applied qdisc & class:

root@testvirt-patrick:~ # tc qdisc sh dev vnet1 qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0 qdisc ingress ffff: parent ffff:fff1 ----------------

SFQ is missing. So I assume you're using and older libvirt (pre 1.0.1). There has been some bugs prior that release ...

root@testvirt-patrick:~ # tc class sh dev vnet1 class htb 1:1 root prio 0 rate 10240Kbit ceil 10240Kbit burst 1598b cburst 1598b

.. notably in setting these burst and cburst values. Try to update and the problem should get resolved. Michal