Enable io_uring support in libuv by default

[ronag]

Couldn’t find any issue tracking this so opening one.

We made ioring opt-in due to security concerns. Do we have any plan to re-enable it?

[lemire]

What are the documented benefits?

[ronag]

libuv/libuv#3952

Performance looks great; an 8x increase in throughput has been observed.

[santigimeno]

We made ioring opt-in due to security concerns. Do we have any plan to re-enable it?

If adding an api in libuv that allows to communicate that user credentials have changed (maybe just thin wrappers over setxid() calls) is acceptable, it certainly can be done.

Also I think we should think thoroughly whether enabling io_uring by default at the moment is a good idea, as there're known issues with the current io_uring implementation in cpu constrained environments (specially relevant for containerized apps).

[ronag]

as there're libuv/libuv#4089 (comment) with the current io_uring implementation in cpu constrained environments (specially relevant for containerized apps).

Isn't that quite easy to work around with a available concurrency check?