PostgreSQL 18 ships three async I/O modes via io_method, and the default is worker, not io_uring. On my cold seq scan benchmark io_uring was the fastest of the three: 1.60s vs 1.88s for worker and 2.65s for sync. Measured on a VM, so treat the ratio as the finding, not the absolute numbers.
Enabling it is one setting plus a restart: sudo -u postgres psql -c "ALTER SYSTEM SET io_method = 'io_uring'" sudo pg_ctlcluster 18 main restart sudo -u postgres psql -tAc 'SHOW io_method' # must print io_uring After enabling, you can watch it actually work. I wrote an eBPF tool (uringscope) that attaches to the kernel's io_uring tracepoints and shows what Postgres submitted, per-request latency, and how many reads detoured through kernel worker threads: curl -LO https://github.com/rch0wdhury/uringscope/releases/latest/download/uringscope-$(uname -m) chmod +x uringscope-$(uname -m) && sudo mv uringscope-$(uname -m) /usr/local/bin/uringscope sudo uringscope -a -d 20 # then run a seq scan in another session Check https://github.com/rch0wdhury/uringscope Disclosure: I'm the author of the tool. -------------- Rajarshi
