[libvirt-users] Strange results with QoS definition

[Patrick Herzfeld]

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

Freundliche Grüsse / kind regards
Patrick Herzfeld

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