[Qemu-devel] Packet dropps in virtual tap interface

[Michael Kazakov]

Hello. We use our highly load system in OpenStack environment. And faced 
with serious problems in network highload guests. At a relatively high 
CPU load of hypervisor (40-60%) virtual network interfaces of this 
guests starts to droppart of the packets. We use for virtualization 
qemu-kvm with vhost driver: "... -netdev 
tap,fd=30,id=hostnet0,vhost=on,vhostfd=31 -device 
virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:86:67:7b,bus=pci.0,addr=0x3...". 

The problem can be seen with the ifconfig utility:
tape4009073-0b Link encap:Ethernet  HWaddr fe:16:3e:86:67:7b
          inet6 addr: fe80::fc16:3eff:fe86:677b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1587622634 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1484106438 errors:0 dropped:460259 overruns:0 
carrier:0
          collisions:0 txqueuelen:500
          RX bytes:877878711500 (877.8 GB)  TX bytes:3071846828531 (3.0 
TB)

Could you do a little look at our problem and give advice which 
direction to continue our investigation?



--
С уважением,
Михаил Казаков
Старший системный администратор
OOO "СПЛАТ"