No VM is running, but 8 of 16 CPUs are in 100% usage in htop

[Saco]

Are enp5s0 and epn6so both connected? If they are both connected to a switch, and you have STP turned off, you could have a bridge loop.

I just removed enp5s0, and only enp6s0 is connected, the issue still there.

 

[Saco]

If you would like to add both interfaces, you have to add a network bonding. Please have a look at the docs: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_network_bond

I added enp5s0 after the issue occurs, just for WebUI to manage PVE from my Mac, and enp6s0 is used to connect to the gateway.
I just removed enp5s0, but the issue still there.

 

[Saco]

was expecting realtek given your symptoms

its possible that alx drivers have issues with kernel ver 6.8; I dont have any hardware with this chip so I cant test, but I would see if the behavior is different on 6.5.

Originally, the issue occurred on an Intel NIC, and then on this Qualcomm one. I can't tell since when, but several weeks ago, there's no issue with both two.