Re: [PATCH] Warn when io_min_workers exceeds io_max_workers

On Mon Jun 22, 2026 at 9:21 PM UTC, Baji Shaik wrote:
> Hi,
>
> Setting io_min_workers to a value greater than io_max_workers is
> silently accepted, but the minimum has no effect and the worker pool
> never grows past io_max_workers. This can confuse users who expect at
> least io_min_workers workers to always be running.
>
> Compare with autovacuum which properly warns:
>
> WARNING: "autovacuum_max_workers" (3) should be less than or equal
> to "autovacuum_worker_slots" (1)
> DETAIL: The server will only start up to "autovacuum_worker_slots" (1)
> autovacuum workers at a given time.
>
> The attached patch adds check_io_worker_gucs() in
> storage/aio/method_worker.c that emits a WARNING similar to what
> autovacuum does for autovacuum_worker_slots vs autovacuum_max_workers:
>
> WARNING: "io_min_workers" (5) should be less than or equal to
> "io_max_workers" (3)
> DETAIL: The I/O worker pool will not exceed "io_max_workers" (3)
> workers.
>
> The check runs in IO worker 0 at startup and after each configuration
> reload.

Baji,

The code looks good. I wonder if we should add a test. I could not find
a similar test for autovacuum for what it's worth.

--
Tristan Partin
PostgreSQL Contributors Team
AWS (https://aws.amazon.com)