[SOLVED] Extremely slow upload speed (1Mbps) in Windows VM

[snflow]

Hi,

I have a Gigabit NIC plugged into a PCI-E slot on my Proxmox server. I also have a Gigabit internet subscription. I created a Windows 11 VM on the Proxmox host and passed the NIC to the Windows VM. The VM can recognize the NIC without any problem. By running Google's internet speed test, I do get the desired download speed from the NIC with about 900Mbps. But I only get 1Mbps of upload speed. I also tried other speed test websites and they all gave similar results. the speedtest.net even gave 0 upload speed. I tried to upload a large file to my Google Drive and it took forever. When I did these tests, I disabled the virtual network bridge from Proxmox. So all the network traffic was handled by this NIC.

When passing through this NIC, I tried to enable or disable the "All function" checkbox and the "PCI-Express" checkbox. But they didn't make any difference.

One thing I noticed was that this NIC does provide Gigabit bandwidth within my local network. I ran the `iperf` test between this Windows VM and my physical Ubuntu desktop. This Windows VM can send and receive data with 950Mbps. So I guess this shouldn't be the driver problem. In fact, the Windows VM does recognize this network connection as "Link speed (Receive/Transmit): 1000/1000 (Mbps)".


I thought this might be a firewall problem. So I tried a lot of firewall settings, I even tried to completely turn off the firewall. But I still get basically zero upload speed. I also checked my router settings but nothing was specially set for this interface.

I'm sure this NIC works fine. To test the NIC, I tried to pass it to another Ubuntu desktop VM where I indeed got the expected speed:


Now I run out of my mind. I really need this NIC to run properly in my Windows VM. Any help or advice will be appreciated.

Thanks!

 

[Dunuin]

You didn't showed us any VM configs. Do you use the default E1000 or the "windows 11 best practice" recommended virtio NIC?

 

[snflow]

You didn't showed us any VM configs. Do you use the default E1000 or the "windows 11 best practice" recommended virtio NIC?

Oops, I forgot to attach my VM config. Apologize. Please see the output of qm config <my_vm_id> below:

agent: 1,freeze-fs-on-backup=0
bios: ovmf
boot: order=scsi0;ide2
cores: 8
cpu: host,flags=+aes
efidisk0: local-lvm:vm-102-disk-0,efitype=4m,pre-enrolled-keys=1,size=4M
hostpci0: 0000:09:00,pcie=1
hostpci1: 0000:07:00,pcie=1
ide2: local:iso/virtio-win-0.1.229.iso,media=cdrom,size=522284K
machine: pc-q35-8.0
memory: 16384
meta: creation-qemu=8.0.2,ctime=1692154571
name: Windows11
net0: virtio=9E:4D:B1:05:10:BF,bridge=vmbr0
numa: 1
ostype: win11
scsi0: local-lvm:vm-102-disk-1,cache=writeback,discard=on,iothread=1,size=256G
scsihw: virtio-scsi-single
smbios1: uuid=0f6726b9-c918-4849-abd7-cd0cc0925f1d
sockets: 1
tpmstate0: local-lvm:vm-102-disk-2,size=4M,version=v2.0
vga: none
vmgenid: 201e6891-e946-4776-a039-6b8a6b52a177

I am following the Windows best practice shown here and using VirtIO as my network device, but it is not relevant to this question. I'm talking about a physical NIC that I plugged into a PCI-E slot and added to my VM using PCI passthrough. When testing this physical NIC, I disabled the VirtIO network interface that comes from the proxmox network bridge.

 

[snflow]

NVM, I found a workaround. Instead of adding the NIC to my VM using PCI-E passthrough, I added a new bridge in proxmox on the NIC and added that bridge to the VM. Now I get full upload and download speed.