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From: Koen De Groote <[email protected]>
To: Thomas Munro <[email protected]>
Cc: PostgreSQL General <[email protected]>
Subject: Re: Running docker in postgres, SHM size of the docker container in postgres 16
Date: Wed, 20 Nov 2024 12:06:07 +0100
Message-ID: <CAGbX52HN8FRkmN6zfAnevFRLw058B59mAEJbghLXeXcK_HZd+g@mail.gmail.com> (raw)
In-Reply-To: <CA+hUKGKKUoS4PDjjP_j6tHRS7jPm=Pu+4Ai56ZT+UWoT2FRcoQ@mail.gmail.com>
References: <CAGbX52GNvsV-sNAS36LwmFOc2Qsn74ZA31T_GNJNeBYATJGBAw@mail.gmail.com>
	<CA+hUKGKKUoS4PDjjP_j6tHRS7jPm=Pu+4Ai56ZT+UWoT2FRcoQ@mail.gmail.com>

That explains a lot.

I have the default of 2 max_parallel_maintenance_workers set, should I set
this to 0?

I realize this is of course an improvement, but working with docker
containers, I'd like to avoid taking /dev/shm away from regular queries.

I assume setting max_parallel_maintenance_workers to 0 is the fix here, is
there perhaps something else I should know about, if I want to have control
over this?

Regards,
Koen De Groote



On Wed, Nov 20, 2024 at 12:38 AM Thomas Munro <[email protected]>
wrote:

> On Wed, Nov 20, 2024 at 11:22 AM Koen De Groote <[email protected]> wrote:
> > Why would that be? It's the exact same data. The install is about 50GB
> in size. Is there something wrong with postgres 16, or did some settings
> significantly change, that I need to know about? I went over all the
> changelogs, nothing stood out as relevant to this, but that might be a lack
> of experience on my end.
>
> Parallel vacuum arrived in PostgreSQL 13, and that uses "dynamic
> shared memory" to share state between workers, and assuming
> dynamic_shared_memory_type=posix, that means shm_open(), which opens
> files under /dev/shm on Linux.
>


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