ixgbe zero-copy performance

Hi,

What is the expected performance for AF_XDP txpnly in zero-copy and copy modes?

With Kernel 6.5.0 and the same ixgbe driver, this is what we see -

ZC mode: 4.3Mpps
Copy mode: 3.3Mpps

This doesn't seem right. Shouldn't the zero copy performance be MUCH higher?

host:~$ sudo ./ubuntu22.04-xdpsock -t -i enp2s0f0 -z

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 2,969,121      2,969,536

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 4,315,534      7,285,632

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 4,315,335      11,601,344

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 4,316,276      15,918,080

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 4,315,285      20,233,920

host:~$ sudo ./ubuntu22.04-xdpsock -t -i enp2s0f0 -c

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 3,326,724      3,327,744

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 3,314,220      6,642,688

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 3,317,285      9,960,448

 sock0@enp2s0f0:0 txonly xdp-drv
                   pps            pkts           1.00
rx                 0              0
tx                 3,323,394      13,284,352

Any thoughts or pointers or things to check for are appreciated!

Srivats