lsr: ls with io_uring

Probably historical preference for portability without a bunch of #ifdef means platform+version-specific stuff is very late to get adopted. Though, at this point, the benefit of portability across various posixy platforms is much lower.

Has anyone written an io_uring "polyfill" library with fallback to standard posix-y IO? It could presumably be done via background worker threads - at a perf cost.

Seems like a huge lift since io_uring is an ever growing set of interfaces that is encompassing more and more of the kernel surface area. Also, the problem tends to not necessarily be that the io_uring interface isn’t available at compile time but a) the version you distribute to has a kernel with it disabled or you don’t have permission to use it meaning you need to do LD_preload magic or use a framework b) the kernel you’re using supports some of the interfaces you’re trying to use but not all. Not sure how you solve that one without using a framework.

But I agree. It would be cool if it was transparent, but this is actually what a bunch of io-uring runtimes do, using epoll as a fallback (eg in Rust monoio)

You can just ask io_uring what commands you have available to you. Though the way of the background thread should be readily available/usable by just indirectly calling the syscall (-helper) and replacing it with a futex-based handshake/wrapper. If you're not using the backend-ordering-imposing link bit, you could probably even use minor futex trickery to dispatch multiple background threads to snatch up from the submission queue in a "grab one at a time" fashion.