I think you missed the point: io_uring is the newer API. Microsoft saw the new async IO API developed for Linux, and made a version for Windows. If what Windows has had all along is so great, why did they bother cloning io_uring when io_uring came along? It definitely isn't because there's any significant body of software relying on io_uring yet.
My theory: people like to extol the virtues of NT's IOCP as "checking the box" for being async, but seldom bother to assess whether the decades-old async API actually offers good performance in comparison to more recent alternatives. But some parts of Microsoft understand quite well that they have pervasive issues with IO performance: replacing WSL1 with WSL2, introducing DirectStorage and a partial copy of io_uring, the Dev Drive feature in Windows 11—all changes that are driven by the understanding that the status quo isn't all that great.
> I think you missed the point: io_uring is the newer API.
GP was pointing out that io_uring came after RIO; RIO has similar capabilities to io_uring for the network space. GP did not "miss the point".
> Microsoft understand quite well that they have pervasive issues with IO performance
This has nothing to do with IOCP but rather the file system filters. This is why removal of file system filters from "DevDrive" (a ReFS volume) improves performance vs a ReFS volume with file system filters in place.
> If what Windows has had all along is so great, why did they bother cloning io_uring when io_uring came along?
IoRing eliminates the need to copy buffers between kernel and user space [0][1].
With regards to performance, this is a bench between a traditional multithreaded UDP server and an RIO IOCP UDP server. The gains are significant. [2] And further comparisons... [3]
> seldom bother to assess whether the decades-old async API actually offers good performance in comparison to more recent alternatives
There are no complete alternatives [r]. Nor is Linux fully asynchronous throughout the kernel.
> introducing DirectStorage
Not really relevant to the context. DirectStorage is a method to deliver data from nVME storage with minimal CPU overhead and/or compressed [4]. Such a system would improve performance on any OS and indeed, we can see that on PS OS (PS5, FreeBSD-based (probably)). Again, limited in scope.
I'm honestly not sure what you're attempting to argue. IoRing brings improvements, yes, but isn't a replacement of IOCP. We should see improvements in any mainstream kernel as a good thing. It's progress. And hopefully the Linux kernel gets to full async I/O at some point in the future.
