From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Tomas Vondra <tomas@vondra.me>, Jelte Fennema-Nio <postgres@jeltef.nl>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Bump soft open file limit (RLIMIT_NOFILE) to hard limit on startup
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Tue, 11 Feb 2025 17:27:09 -0500"
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Date: Tue, 11 Feb 2025 17:55:39 -0500
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Andres Freund <andres@anarazel.de> writes:
> In the current version of the AIO patchset, the creation of those io_uring
> instances does happen as part of an shmem init callback, as the io uring
> creation also sets up queues visible in shmem.

Hmm.

> So the issue would actually be that we're currently doing set_max_safe_fds()
> too late, not too early :/

Well, we'd rather set_max_safe_fds happen after semaphore creation,
so that it doesn't have to be explicitly aware of whether semaphores
consume FDs.  Could we have it be aware of how many FDs *will be*
needed for io_uring, but postpone creation of those until after we
jack up RLIMIT_NOFILE?

I guess the other way would be to have two rounds of RLIMIT_NOFILE
adjustment, before and after shmem creation.  That seems ugly but
shouldn't be very time-consuming.

			regards, tom lane