Xdp in run to completion and poll mode

[Adarsh97]

I am having an observation where in some of the system with optical fiber adapter (sfp/sfp+) the run to completion mode is not working, only the poll mode is working.
In run to completion I am unable to see any packet received in the user space.
Is this expected ?
Can we have a solution for this?
Or any network setting I have to change
@magnus-karlsson @tohojo @dmitris @donaldh @netoptimizer

[magnus-karlsson]

With that sparse information you provided anything could be wrong. You have to submit enough information for someone else to reproduce your problem, otherwise we cannot help you.

[Adarsh97]

I understand that.
First of all is the above behaviour expected by design ?
If it is not I will try to debug it further.

[magnus-karlsson]

Again, unfortunately depends on what you are doing :-). An Rx only workload can run without any syscalls. If you have a Tx only workload, then you need syscalls. If you have both, then you can generally run without any syscalls. But if you are using the need_wakeup feature, then processing might stop and you need to wakeup the driver with a syscall such as poll(), recvmsg(), or sendto(). Without need_wakeup on, the driver will busy-loop at 100% requiring no syscalls in zero-copy mode.