XDP is not for every use-case.
Important to understand¶
It is important to understand that the XDP speed gains comes at a cost of loss of generalization and fairness.
XDP does not provide fairness. There is no buffering (qdisc) layer to absorb traffic bursts when the TX device is too slow, packets will simply be dropped. Don’t use XDP in situations where the RX device is faster than the TX device, as there is no back-pressure to save the packet from being dropped. There is no qdisc layer or BQL (Byte Queue Limit) to save you from introducing massive bufferbloat.
Using XDP is about specialization. Crafting a solution towards a very specialized purpose, that will require selecting and dimensioning the appropriate hardware. Using XDP requires understanding the dangers and pitfalls, that come from bypassing large parts of the kernel network stack code base, which is there for good reasons.
That said, XDP can be the right solution for some use-cases, and can yield huge (orders of magnitude) performance improvements, by allowing this kind of specialization.