Thanks, So you're saying a retransmit is not observed specifically when you're bursting traffic, but it is more random on normal load?
What flow steering mode are you using ? you can check dmesg when the driver loads or copy paste content in /etc/modrporbe.d/mlnx.conf
Can you capture /proc/interrupts supposedly when you see a retransmit counter increment in netstat ?
is FC enabled on switches ?