It's been a while but why is uring not helpful for larger buffers? I'd think the zero-copy I/O capabilities would make it more helpful for larger payloads, not less
uring supports zero-copy, but is not a copy-reduction mechanism; it is a syscall-reduction mechanism. Large buffers mean less syscalls to start with, so less benefit.
Exactly this. The kernel alloc’d buffers can help but if that was a primary concern you’re in driver territory. Anything still userspace kind of optimization domain the portion of syscalls for large buffers in a buffered flow is heavily amortized and not overly relevant.