Waiting for Postgres 18: Accelerating Disk Reads with Asynchronous I/O
a year ago
- #Performance
- #Postgres
- #Cloud
- Postgres 18 introduces Asynchronous I/O (AIO) for read operations, a significant architectural shift aimed at improving performance, especially in cloud environments.
- Asynchronous I/O allows Postgres to issue multiple read requests concurrently, reducing latency by not waiting for each read to complete before proceeding.
- Postgres 18 introduces a new configuration parameter, `io_method`, with three settings: `sync` (traditional synchronous I/O), `worker` (uses dedicated I/O workers), and `io_uring` (Linux-specific, high-performance I/O interface).
- Benchmarks on AWS show that asynchronous I/O can double read performance, with `io_uring` delivering the best results by reducing syscall overhead.
- The `effective_io_concurrency` parameter becomes more impactful in Postgres 18, directly controlling read-ahead requests when using asynchronous I/O methods.
- New monitoring tools like `pg_aios` view help track I/O operations in flight, especially useful with asynchronous I/O where traditional monitoring may not capture all I/O activity.
- Asynchronous I/O changes how I/O timing is reported in `EXPLAIN ANALYZE`, potentially underreporting I/O effort, requiring adjustments in performance analysis practices.
- Future Postgres versions may expand asynchronous I/O to include write operations, further optimizing performance for modern workloads.