Is that true for all file abstractions? What happens with NFS?

    Note that this flag has no effect for regular files and block devices; that is, I/O operations will (briefly) block when device activity is required, regardless  of  whether O_NONBLOCK  is  set.  Since O_NONBLOCK semantics might eventually be implemented, applications should not depend upon blocking behavior when specifying this flag for regular files and block devices.

Some people would rather have an abstraction over io_uring and kqueue rather than choosing a single API that works everywhere they want to run, choosing to only run on the OS that provides the API they prefer, or writing their loop (and anything else) for all the APIs they want to support.

But I agree with you; I'd rather use the thing without excess abstraction, and the standard apis work well enough for most applications. Some things do make sense to do the work to increase performance though.

In the real world, unless are writing a very specialized system, intended to run only on Linux 6.0 and never, it just is not realistic and you will need some sort of abstraction layer to support at the very least additionally poll to be portable across all POSIX and POSIX like systems. Then if you want your thing to also run on Windows, IOCP rides in too...

I used 6.0 because 5.8-5.9 is roughly when io_uring became interesting to use for most use cases with zero copies, prepared buffers and other goodies, and 6.0 is roughly when people finally started being able to craft benchmarks where io_uring implementations beat epoll.

Also, the Zig 0.16.0 preview nightly builds includes a new Io library[0]. I have not used libxev or Tigerbeetles event loop, but I believe the standard Zig implementation is likely largely influenced by those two.

[0] https://ziglang.org/documentation/master/std/#std.Io, or https://ziglang.org/documentation/0.16.0/std/#std.Io after the release

I’m curious, how do you know it was inspired by tiger beetles impl?

They look very similar so that makes sense, just curious on the order of events.

Also I tried using libxev for a project of mine and found it really broke the zig way of doing things. All these callbacks needed to return disarm/rearm instead of error unions so I had to catch every single error instead of being able to use try.

I could have reworked it further to make try work but found the entire thing very verbose and difficult to use with 6 params for all the callback functions.

Thankfully my use case was such that poll() was more than sufficient and that is part of zigs posix namespace so that was what I went with.

I recently created this, which is largely based on ideas from libxev, but my optimized for my zio runtime. https://github.com/lalinsky/aio.zig

kqueue is similar to epoll, it's readiness based and not completion like IOCP and io_uring. IOCP is nice in theory, but the api and the different ways everything has to be fed for it leaves a lot to be desired... Windows also has own version of iouring, but it's bit abandoned and only works for disk io which is shame, because it could have been nice new clean io api for windows.

I’ve been enjoying the rust compio library lately which abstracts over io_uring on Linux. And IOCP and friends on windows. And it falls back to kqueue on macOS and presumably FreeBSD.

It’s wonderful being able to write straightforward code that works fast on every platform with no code changes.

I guess the strength of rust (and zig for now) is that the community has a chance to explore lots of different ways to solve these problems. And the corresponding weakness is that everyone uses different libraries, so it’s a fragmented ecosystem full of libraries that may or may not work together properly.

I've only done a little prototyping with it, but io_uring addresses the same issue as DPDK, but in a totally different way. If you want high perf, you want to avoid context switches between userland and kernelland; you have DPDK which brings the NIC buffers into userland and bypasses the kernel, you have things like sendfile and kTLS which lets the kernel do most of the work and bypasses userland; and you have io_uring which lets you do the same syscalls as you're doing now, but a) in a batch format, b) also in a continuous form with a submission queue thing. I think it's easier to reach for io_uring than DPDK, but it might not get you as far as DPDK; you're still communicating between kernel and userland, but it's better than normal syscalls.

> Can you get similar performance with QUIC?

I don't know that I've seen benchmarks, but I'd be surprised if you can get similar performance with QUIC. TCP has decades of optimization that you can lean on, UDP for bulk transfer really doesn't. For a lot of applications, server performance from QUIC vs TCP+TLS isn't a big deal, because you'll spend much more server performance on computing what to send than on sending it... For static file serving, I'd be surprised if QUIC is actually competitive, but it still might not be a big deal if your server is overpowered and can hit the NIC limits with either.

At least to me, one of the most compelling parts of QUIC is that you establish a connection with TLS without needing extra round trips compared to TCP, where there are separate handshakes for the connection and then the TLS initialization. Even if it was no faster than TCP from that point forward, that seems like enough to make the protocol worthwhile in today's world where TLS is the basically the rule with relatively few exceptions rather than an occasion use case.

It's also something I just find fascinating because it's one of the few practical cases where I feel like the compositional approach has what seems to be an insurmountable disadvantage compared to making a single thing more complex. Maybe there are a lot more of them that just aren't obvious to me because the "larger" thing is already so well-established that I wouldn't consider breaking it into smaller pieces because of the inherent advantage from having them combined, but even then it still seems surprising that that gold standard for so long arguably because of how well it worked with things that came after eventually run into change in expectations that it can't adapt to as well as something with intentionally larger scope to include one of those compositional layers.

It still does not hook up to seccomp, so needs to be blocked by things doing syscall filtering. Its blocked by docker/podman. It may also be disabled with hardened kconfig or selinux.

If it ever integrates with LSMs, then it may be time to give it another look.