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

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(a)upx.com&gt; 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/wik >> i/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/pag >> e/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(a)ovirt.org >> http://lists.ovirt.org/mailman/listinfo/users >> >> > > > >