examples/io_uring-udp.c: IORING_SETUP_COOP_TASKRUN is incompatible with （IORING_SETUP_SQPOLL | IORING_SETUP_SQ_AFF）?

[hi-glenn]

https://github.com/axboe/liburing/blob/liburing-2.3/examples/io_uring-udp.c#L98

After replace the following code chunk

params.flags = IORING_SETUP_SUBMIT_ALL | IORING_SETUP_COOP_TASKRUN |
		       IORING_SETUP_CQSIZE;

with

params.flags = IORING_SETUP_SUBMIT_ALL | IORING_SETUP_COOP_TASKRUN |
		       IORING_SETUP_CQSIZE | IORING_SETUP_SQPOLL | IORING_SETUP_SQ_AFF;

params.sq_thread_idle = 10;
params.sq_thread_cpu = 1;

I get the error code：-22; and error info is Invalid argument.

My test environment is as the following:

Operating System: Ubuntu 22.04.1 LTS              
          Kernel: Linux 6.2.2-060202-generic
    Architecture: x86-64

Is my usage correct?

[isilence]

Right, IORING_SETUP_COOP_TASKRUN is not compatible with IORING_SETUP_SQPOLL, and it wouldn't make sense to set them together. Not sure if it's obvious from manuals.

[AomaYple]

Right, IORING_SETUP_COOP_TASKRUN is not compatible with IORING_SETUP_SQPOLL, and it wouldn't make sense to set them together. Not sure if it's obvious from manuals.

So which is more recommended to use (based on performance)

[axboe]

SQPOLL is a pretty specialized mode, not a default kind of thing. COOP_TASKRUN is fine. DEFER_TASKRUN is usually preferred if it works with the model, requiring single task/thread per ring. See the wiki page on networking for details.

[AomaYple]

COOP_TASKRUN

So is COOP_TASKRUN better if the model is per thread per ring (these rings are independent and don't affect each other)

[axboe]

As mentioned, usually defer TASKRUN would be preferable.

[AomaYple]

As mentioned, usually defer TASKRUN would be preferable.

Thank you!