On Mon, 15 Nov 2021 11:13:44 +0100 Clément Léger wrote:

Test on standard packets with UDP (iperf3 -t 100 -l 1460 -u -b 0 -c *)
- With pre-computed header: UDP TX: 	33Mbit/s
- Without UDP TX: 			31Mbit/s
-> 6.5% improvement  

Test on small packets with UDP (iperf3 -t 100 -l 700 -u -b 0 -c *)
- With pre-computed header: UDP TX: 	15.8Mbit/s
- Without UDP TX: 			16.4Mbit/s
-> 4.3% improvement  

Something's wrong with these numbers or I'm missing context.
You say improvement in both cases yet in the latter case the 
new number is lower?