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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: Andres Freund <andres@anarazel.de>
Cc: "Imseih (AWS), Sami" <simseih@amazon.com>, Justin Pryzby <pryzby@telsasoft.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2024-06-18T19:00:00Z
Lists: pgsql-hackers 
On Mon, Jun 03, 2024 at 04:24:27PM -0700, Andres Freund wrote:
> On 2024-06-03 14:28:13 -0500, Nathan Bossart wrote:
>> On Mon, Jun 03, 2024 at 12:08:52PM -0700, Andres Freund wrote:
>> > Why do we think that increasing the number of PGPROC slots, heavyweight locks
>> > etc by 256 isn't going to cause issues?  That's not an insubstantial amount of
>> > memory to dedicate to something that will practically never be used.
>> 
>> I personally have not observed problems with these kinds of bumps in
>> resource usage, although I may be biased towards larger systems where it
>> doesn't matter as much.
> 
> IME it matters *more* on larger systems. Or at least used to, I haven't
> experimented with this in quite a while.
> 
> It's possible that we improved a bunch of things sufficiently for this to not
> matter anymore.

I'm curious if there is something specific you would look into to verify
this.  IIUC one concern is the lock table not fitting into L3.  Is there
anything else?  Any particular workloads you have in mind?

-- 
nathan

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.