[ovirt-users] Strange network performance on VirtIIO VM NIC

[FERNANDO FREDIANI]

Hello Yaniv.

Have a new information about this scenario: I have load-balanced the 
requests between both vNICs, so each is receiving/sending half of the 
traffic in average and the packet loss although it still exists it 
lowered to 1% - 2% (which was expected as the CPU to process this 
traffic is shared by more than one CPU at a time).
However the Load on the VM is still high probably due to the interrupts.

Find below in-line the answers to some of your points:


On 21/03/2017 12:31, Yaniv Kaul wrote:
>
> So there are 2 NUMA nodes on the host? And where are the NICs located?
Tried to search how to check it but couldn't find how. Could you give me 
a hint ?
>
> BTW, since those are virtual interfaces, why do you need two on the 
> same VLAN?
Very good question. It's because of an specific situation where I need 
to 2 MAC addresses in order to balance the traffic in LAG in a switch 
which does only layer 2 hashing.
> Are you using hyper-threading on the host? Otherwise, I'm not sure 
> threads per core would help.
Yes I have hyper-threading enabled on the Host. Is it worth to enable it ?

Thanks
Fernando

>>
>>     On 18/03/2017 12:53, Yaniv Kaul wrote:
>>>
>>>
>>>     On Fri, Mar 17, 2017 at 6:11 PM, FERNANDO FREDIANI
>>>     <fernando.frediani at upx.com <mailto:fernando.frediani at upx.com>>
>>>     wrote:
>>>
>>>         Hello all.
>>>
>>>         I have a peculiar problem here which perhaps others may have
>>>         had or know about and can advise.
>>>
>>>         I have Virtual Machine with 2 VirtIO NICs. This VM serves
>>>         around 1Gbps of traffic with thousands of clients connecting
>>>         to it. When I do a packet loss test to the IP pinned to NIC1
>>>         it varies from 3% to 10% of packet loss. When I run the same
>>>         test on NIC2 the packet loss is consistently 0%.
>>>
>>>         From what I gather I may have something to do with possible
>>>         lack of Multi Queu VirtIO where NIC1 is managed by a single
>>>         CPU which might be hitting 100% and causing this packet loss.
>>>
>>>         Looking at this reference
>>>         (https://fedoraproject.org/wiki/Features/MQ_virtio_net
>>>         <https://fedoraproject.org/wiki/Features/MQ_virtio_net>) I
>>>         see one way to test it is start the VM with 4 queues (for
>>>         example), but checking on the qemu-kvm process I don't see
>>>         option present. Any way I can force it from the Engine ?
>>>
>>>
>>>     I don't see a need for multi-queue for 1Gbps.
>>>     Can you share the host statistics, the network configuration,
>>>     the qemu-kvm command line, etc.?
>>>     What is the difference between NIC1 and NIC2, in the way they
>>>     are connected to the outside world?
>>>
>>>
>>>         This other reference
>>>         (https://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature
>>>         <https://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature>)
>>>         points to the same direction about starting the VM with queues=N
>>>
>>>         Also trying to increase the TX ring buffer within the guest
>>>         with ethtool -g eth0 is not possible.
>>>
>>>         Oh, by the way, the Load on the VM is significantly high
>>>         despite the CPU usage isn't above 50% - 60% in average.
>>>
>>>
>>>     Load = latest 'top' results? Vs. CPU usage? Can mean a lot of
>>>     processes waiting for CPU and doing very little - typical for
>>>     web servers, for example. What is occupying the CPU?
>>>     Y.
>>>
>>>
>>>         Thanks
>>>         Fernando
>>>
>>>
>>>
>>>         _______________________________________________
>>>         Users mailing list
>>>         Users at ovirt.org <mailto:Users at ovirt.org>
>>>         http://lists.ovirt.org/mailman/listinfo/users
>>>         <http://lists.ovirt.org/mailman/listinfo/users>
>>>
>>>
>>
>>
>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ovirt.org/pipermail/users/attachments/20170321/e4c3edc7/attachment-0001.html>