Try testing it with a local connection using iperf3
Just curious: what system are you using?
Normally you should also be affected (I mean if you are using OpenWRT). By disabling sqm, I got 40% of the maximum upload bandwidth.
Archlinux Arm on BPI-R3 mostly
So definitely there is an issue with YT8821 and OpenWRT Snapshot (24.10) that is working on kernel 6.6.
For connection LAN<->WAN (network 1/1 Gbps, HW offload), I have 940/938Mbps (so it is correct).
For connection Wireless<->WAN(network 1/1Gbps, HW offload, WO disabled, AX, 160Mhz, 5GHz), I have 860/210Mbps (where testing network via iperf3 or librespeed-go that is running on the BPI-R4, for local connection I have 1640/1100Mbps, so definitely it is not wireless issue).
To get better performance, I can enable SQM with fq_codel + piece_of_cake, then the results are 908/730Mbps. I have done many speed tests, many tests even for dedicated servers - each time results are same.
So when I switch back to use port WAN (not sfp one), results are 915/890Mbps. I just want to share the results with others. Maybe it will help someone to avoid buying SFP with that chipset (for now).
EDIT:
Found temporary “solution”: enabling flow control (ethtool -A eth2 rx on tx on) seems to improve upload, but download goes slower - I can accept that. Finally results after enabling flow control: 850/940Mbps
To make flow control enabled after upgrade:
cat <<EOF > /etc/rc.local
if ethtool -a eth2 | grep -i rx | grep -q off; then echo "Setting flow control..."; ethtool -A eth2 rx on tx on; ip link set eth2 down; sleep 2; ip link set eth2 up ; fi
exit 0
EOF
after the last major netifd update. flow control for sfp can be set using the network config file. cleaner.
config device
option name 'eth2'
option rxpause '1'
option txpause '1'
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