linux vmxnet3 seriously broken in esxi 4.1

[Atmos4]

Hi,

I'm seeing a strange problem after upgrading hosts from ESXi 4.0.1 to 4.1: Upload bandwidth from the physical to the vm network for Linux VMs using VMXNET3 is throttled at around 1 MBit, while downstream is unaffected at around 940 MBit/s. Tested with iperf on xp client and linux server.

When running iperf between XP VM and the same Linux VM with VMXNET3 I get 350 Mbps upstream.

If I switch the VM to e1000, upstream from physical network jumps to 400 MBps with downstream still at around 940 Mbps.

I repeated this test with another linux VM, also running Debian Lenny x86_64 with same result.

Anyone else seeing this problem? Is there a fix?

The affected VM acts as a router between several GBit VLANs, so this is a really big issue.

Regards,

Felix Buenemann

[Atmos4]

OK, the problem seems to be caused by LRO, so I disabled it:

Create a file /etc/modprobe.d/vmxnet3.conf with content:

\# disable LRO, because it causes throttling of incoming traffic

options vmxnet3 disable_lro=1

After that I ran update-initramfs -u (probably not needed) and rebootet the host.

Now incoming speed is back to 370 Mbps with a single stream and 910 Mbps with 4 parallel streams.