> Do you think there's a possibility of Direct IO being adopted at some point in the future now that AIO is available?

Explicitly a goal.

You can turn it on today, with a bunch of caveats (via debug_io_direct=data). If you have the right workload - e.g. read only and lots of seqscans, bitmap index scans etc you can see rather substantial perf gains. But it'll suck in any cases in 18.

We need at least:

- AIO writes in checkpointer, bgwriter and backend buffer replacement (think bulk loading data with COPY)

- readahead support in a few more places, most crucially index range scan (works out ok today if the heap is correlated with the index, sucks badly otherwise)

EDIT: Formatting