Greeting,
Could you advise on how to change or configure the virtual ethernet driver?
Recently, I tested network performance inside a VM using iperf3.
The test results are attached below.
As shown in the screenshot, a high number of retransmissions occurred. I suspect this might be a driver or NIC offload issue.
Any suggestions would be greatly appreciated. I am still searching for a fix.
Thanks!
**For good communication, I used AI Power.
Summary of Findings:** I have been troubleshooting high TCP retransmissions in an Incus VM connected to a Linux bridge, comparing its performance to a pure KVM environment.
The core solution to the initial retransmission issue is disabling network offloading on the guest VM interface. sudo ethtool -K eth0 tso off gso off gro off
Issue: When the MTU is increased to 9000 (Jumbo Frames), retransmissions occur. However, the retransmission count is consistently fixed at exactly 28 during a standard 10-second iperf3 test. This fixed value of 28 persists uniformly even when testing against different receiving hardware.
Question: Is there a specific method or tuning parameter to completely reduce retransmissions to 0 when using MTU 9000 even 1500. in an Incus VM? I would appreciate any advice regarding QEMU/vhost configuration, TAP buffer sizing, or kernel networking parameters to resolve this final bottleneck.
In case of SR-IOV, PCI Passthrough, we must set tso, gso, gro to ON to use hardware acceleration.
