[ovs-discuss] UDP loss rate in OVS 2.5

[Jeroen Van Bemmel]

Hi Amru,
Iperf is notoriously poor at measuring UDP performance, as packets get lost in the tool itself. Look at CPU usage and you may see what's going on

Try nuttcp instead - I dont think this is an OVS issue

Regards,
Jeroen

Sent from my iPhone

> On Jul 2, 2016, at 09:54, Amru OM <sdn.innovation at gmail.com> wrote:
> 
> Greetings,
> 
>  
> 
> I have installed the latest OVS 2.5 in each physical server of my testbed. The physical servers running CentOS Linux release 7.2.1511 as the host operating system. Also, each host has one VM running via KVM.  The VM in each server is connected to OVS through vNIC (e.g., tap0). Here is the command line that I used to configure and start-up the VMs
> 
>  
> 
> qemu-kvm -m 2048 -netdev tap,id=hostnet0,script=/etc/ovs-ifup,downscript=/etc/ovs-ifdown,vhost=on -device virtio-net-pci, netdev=hostnet0,id=net0,mac=52:54:00:af:87:57,bus=pci.0,addr=0x3 -drive file=/var/lib/libvirt/images/fedora.img -cpu host -smp cores=1,threads=2
> 
>  
> 
> the OVS (in each server) and the host NIC are configured as follows:
> 
>  
> 
> ovs-vsctl add-br br0
> 
> ovs-vsctl add-port br0 eth0
> 
> ifconfig eth0 0 up
> 
> ifconfig br0 10.0.0.x netmask 255.0.0.0 up
> 
>  
> 
> eth0 above-mentioned is the physical NIC in the host and its link-speed is 56 Gbits/sec.
> 
>  After configuring and running OVS and VM in each host, I tested the bandwidth between two VMs located in different hosts via Iperf. When I test the UDP bandwidth, where packets have large payload ( >= 10KB), the test results show high packet loss rate.  For example, when I run Iperf as follows:
> 
>  
> 
> Iperf  -u -c 10.0.0.x  -l 10K  -b 56G
> 
>  
> 
> The test result of UDP bandwidth is 2.88 Gbits/sec, and packet loss rate ~ 72%. This poor performance only occurs with UDP, but not with TCP. I just wonder if I’m missing something here.
> 
>  
> 
>  
> 
> Please advise and thank you in advance.
> 
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