APU2c4 with 19.07 poor ethernet performance

Hello everyone.
I need help troubleshooting my new router setup. It's an APU2c4 with WLE900VX, latest bios and freshly installed OpenWRT 19.07, following instructions on teklager.se.
I checked the wired ethernet connection with iperf3, and it tops out at little over 300Mbps, both LAN and WAN (I have a 750Mbps cable connection). Even the wireless connection works better than that. Could anyone provide some help with troubleshooting?

even though not for openwrt, this might still be relevant

@frollic , unfortunately, LuCI doesn't present such settings. Is there a way to set them via console?

check out Netfilter "Flow offload" / HW NAT

it get interesting around post 50 :wink:

I found offloading settings in the firewall section, but neither software nor hardware offloading did anything for me. I checked with the wireless adapter unplugged and the issue still persists. I think I'll reinstall openWRT tomorrow, or maybe check with IPFire if that's a hardware or software problem.

I came back with more findings.
Running iperf3 server on any of the LAN devices, the router iperf3 client maintains a 1Gb-ish link.
However, with iperf3 server on the router, LAN clients only go up to 300-330Mb.
With one LAN iperf3 server and one LAN iperf3 client, the connection speed between them is still 300-330Mb.
Seems like something is bottlenecking router-incoming traffic. It's not supposed to be like that, right?
My topology is: ISP cable modem (modem/router set in bridge mode) -> APU2c4 router -> LAN devices.
I might check earlier OpenWrt versions next. If all else fails, I might end up using the APU2 as just an access point, since wifi problems were my main reason for upgrading.

I am interested in this device and thus concerned about the issue.

Did you get it sorted?

Can you check if you have irqbalance installed and running?