In general should virtual functions outperform virtio+vhost for
networking performance - latency and throughput?
I have 2 VMs running on a host. Each VM has 2 nics -- one tied to a VF
and the other going through virtio and a tap device like so:
------ ----
| |----------------| VF |---
| | ---- |
| VM 1 | |
| | ----- |
| |---| tap |--- |
------ ----- | ---
--- | e |
| b | | t |
| r | | h |
--- | 2 |
------ ----- | ---
| |---| tap |--- |
| | ----- |
| VM 2 | |
| | ---- |
| |----------------| VF |---
------ ----
The network arguments to qemu-kvm are:
-netdev type=tap,vhost=on,ifname=tap2,id=netdev1
-device virtio-net-pci,mac=${mac},netdev=netdev1
where ${mac} is unique to each VM and for the VF:
-device pci-assign,host=${pciid}
netserver is running within the VMs, and the netperf commands I am
running are:
netperf -p 12346 -H <ip> -l 20 -jcC -fM -v 2 -t TCP_RR -- -r 1024
netperf -p 12346 -H <ip> -l 20 -jcC -fM -v 2 -t TCP_STREAM
where <ip> changes depending on which interface I want to send the
traffic through. To say the least results are a bit disappointing for
the VF:
latency throughput
(usec/Tran) (MB/sec)
Host-VM
over virtio 139.160 1199.40
over VF 488.124 209.22
VM-VM
over virtio 322.056 773.54
over VF 488.051 328.88
I am just getting started with VFs and could use some hints on how to
improve the performance.
Host:
Dell R410
2 quad core E5620@xxxx GHz processors
16 GB RAM
Intel 82576 NIC (Gigabit ET Quad Port)
Fedora 14
kernel: 2.6.35.12-88.fc14.x86_64
qemu-kvm-0.13.0-1.fc14.x86_64
VMs:
Fedora 14
kernel 2.6.35.11-83.fc14.x86_64
2 vcpus
1GB RAM
Thanks,
David
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