I think what you're trying to accomplish is a factor here.

If you just want to saturate the bandwidth, to move some coherent blob of data from point A to point B as fast as possible (say you're implementing the `cp` command), then using large buffers is the best and easiest way. Small buffers confer no additional benefit other than driving more complicated designs, forcing io_uring with registered buffers and fds, etc.

If you want to maximize IOPS, then by the fact that we just established that large buffers saturate the bandwidth better, small buffers is the only viable option, but then you need to whittle down the per-read overhead, and end up with io_uring or even more specialized tools.