13.7. Optimizing virtual machine network performance
Due to the virtual nature of a VM’s network interface card (NIC), the VM loses a portion of its allocated host network bandwidth, which can reduce the overall workload efficiency of the VM. The following tips can minimize the negative impact of virtualization on the virtual NIC (vNIC) throughput.
Procédure
Use any of the following methods and observe if it has a beneficial effect on your VM network performance:
- Enable the vhost_net module
On the host, ensure the
vhost_netkernel feature is enabled:# lsmod | grep vhost vhost_net 32768 1 vhost 53248 1 vhost_net tap 24576 1 vhost_net tun 57344 6 vhost_netIf the output of this command is blank, enable the
vhost_netkernel module:# modprobe vhost_net- Set up multi-queue virtio-net
To set up the multi-queue virtio-net feature for a VM, use the
virsh editcommand to edit to the XML configuration of the VM. In the XML, add the following to the<devices>section, and replaceNwith the number of vCPUs in the VM, up to 16:<interface type='network'> <source network='default'/> <model type='virtio'/> <driver name='vhost' queues='N'/> </interface>If the VM is running, restart it for the changes to take effect.
- Batching network packets
In Linux VM configurations with a long transmission path, batching packets before submitting them to the kernel may improve cache utilization. To set up packet batching, use the following command on the host, and replace tap0 with the name of the network interface that the VMs use:
# ethtool -C tap0 rx-frames 64- SR-IOV
- Si votre carte réseau hôte prend en charge SR-IOV, utilisez l'affectation de périphériques SR-IOV pour vos cartes réseau virtuelles. Pour plus d'informations, voir Gestion des périphériques SR-IOV.
Ressources supplémentaires
