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Re: allow changing autovacuum_max_workers without restarting

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: "Imseih (AWS), Sami" <simseih@amazon.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2024-04-11T19:24:23Z
Lists: pgsql-hackers 
On Thu, Apr 11, 2024 at 03:37:23PM +0000, Imseih (AWS), Sami wrote:
>> My concern with this approach is that other background workers could use up
>> all the slots and prevent autovacuum workers from starting
> 
> That's a good point, the current settings do not guarantee that you
> get a worker for the purpose if none are available, 
> i.e. max_parallel_workers_per_gather, you may have 2 workers planned 
> and 0 launched. 
> 
>> unless of
>> course we reserve autovacuum_max_workers slots for _only_ autovacuum
>> workers. I'm not sure if we want to get these parameters tangled up like
>> this, though...
> 
> This will be confusing to describe and we will be reserving autovac workers
> implicitly, rather than explicitly with a new GUC.

Yeah, that's probably a good reason to give autovacuum its own worker pool.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Give up on running with NetBSD/OpenBSD's default semaphore settings.

  2. initdb: Do not report default autovacuum_worker_slots.

  3. Lower default value of autovacuum_worker_slots in initdb as needed.

  4. Allow changing autovacuum_max_workers without restarting.

  5. Reserve a PGPROC slot and semaphore for the slotsync worker process.

  6. Make archiver process an auxiliary process.

  7. Correct the formulas for System V IPC parameters SEMMNI and SEMMNS in docs.