Re: Potential "AIO / io workers" inter-worker locking issue in PG18?

Hi,

On 2025-10-05 10:55:01 +0200, Marco Boeringa wrote:
> This has worked really well in previous versions of PostgreSQL (tested up to
> PG17). However, in PG18, during the multi-threaded processing, I see some of
> my submitted jobs that in this case were run against a small OpenStreetMap
> Italy extract of Geofabrik, all of a sudden take > 1 hour to finish (up to 6
> hours for this small extract), even though similar jobs from the same
> processing step, finish in less than 10 seconds (and the other jobs should
> as well). This seems to happen kind of "random". Many multi-threading tasks
> before and after the affected processing steps, do finish normally.
> 
> When this happens, I observe the following things:
> 
> - High processor activity, even though the jobs that should finish in
> seconds, take hours, all the while showing the high core usage.
> 
> - PgAdmin shows all sessions created by the Python threads as 'active', with
> *no* wait events attached.

I think we need CPU profiles of these tasks. If something is continually
taking a lot more CPU than expected, that seems like an issue worth
investigating.

Greetings,

Andres Freund