UDP Checksum offload with X550-T2

Stephen Hemminger stephen at networkplumber.org
Fri Feb 7 23:52:11 CET 2025


On Fri, 7 Feb 2025 17:34:47 -0500
Alan Beadle <ab.beadle at gmail.com> wrote:

> Apparently I just needed to increase the TX ring size. I'm still
> having trouble getting anywhere close to the theoretical 10 gigabit
> bandwidth of my NIC without running into TX failures. Should that be
> feasible with an MTU of 1514 bytes? I'm not even taxing the CPU very
> much now that checksum offload is working.

Remember that 10 gigabit includes all the other overheads like headers, inter-frame gap etc.
MTU is usually expressed independent of headers.
	
	Interframe gap = 96 bits = 12 bytes
	max frame size = 1518 bytes (Ether + MTU + CRC)

If you are using IP + UDP need to subtract those headers as well.
Which means 1500 becomes 1440 bytes.

With DPDK, the transmit cleanup is controlled via tx_free_thresh
which may need adjust as well.


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