The rapid growth of io_uring

> So now that Linux is moving in the direction of increasingly complex, leaky APIs to cover the performance gap, treading the old waters of enterprise Unix, what does that imply, if anything, about the evolution of Linux and the state of hardware.

What it says about the state of hardware is easy.

Meltdown mitigations made context switching more expensive, and SSDs made the actual I/O cheaper. At some point, you're spending almost as much time context switching as you are doing actual work, and there's nothing Linux can do about it because it's all tied up in the architecture of the MMU and the processor's cache. Thus, it now makes sense to design the interface around reducing the number of context switches at all cost, instead of just assuming that the cost of doing the actual I/O will dominate.