Re: Network Overruns

[Avi Kivity <avi@qumranet.com>]

xming wrote:
>> Most likely the guest's rx queue length is greater than the host's.  You
>> might try
>>
>>   ifconfig vnet0 txqueuelen 1500
>>
>> (and so on for every interface)
>>
>>
>> or perhaps reducing the guests' txqueuelen.
>>     
>
> I have the same issue (overruns) and I have stalled network (in my other
> report I can only unstall the network by putting the NIC in promisc back
> and forth).
>
> The txqueuelen is indeed greater in the guest then the tap on the host,
> and I also notice that it's almost ways the output NIc which get stuck.
>
> So changing the tap (on the host) to 1500, I can't not reproduce the hang yet
> and a ping -f -s 64000 (between guests) does not produce any packet loss.
>
> 27810 packets transmitted, 27809 received, 0% packet loss, time 259080ms
> rtt min/avg/max/mdev = 5.013/7.639/33.999/1.536 ms, pipe 3, ipg/ewma
> 9.316/7.284 ms
>
> I hope this is the solution for my network stalls and packet loss in games.
>   

It's not a fix, rather a workaround.  Hopefully some networking guru
will come up with a real fix.

What NIC model are you using in the guest?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.