How to improve the throughput of a device using AM5716 CPU?

I have this customized device that is using an AM5716 CPU and installed with OpenWrt snapshot r14777-c4ab1b7dd9, I tried to run iperf3 test on it and my PC in order to test the maximum throughput.

on the device: iperf3 -s
on my PC: iperf3 -c
Result: around 790Mbps ~ 830Mbps

on my PC: iperf3 -c -R
Result: around 940Mbps

Any idea why this happens? Is there any way to boost up the throughput of the device?

You shouldn't be using your device as an endpoint with iperf, and you are.

The way to run a throughput test is Iperf server <----------> OpenWrt device <-------------> Iperf client.