Feedback-ID: id4a34324:Fastmail
Date: Tue, 11 Feb 2025 14:42:21 -0500
From: Andres Freund <andres@anarazel.de>
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Bump soft open file limit (RLIMIT_NOFILE) to hard limit on
 startup
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Hi,

On 2025-02-11 19:52:34 +0100, Jelte Fennema-Nio wrote:
> So this starts bumping postmaster and pgbench its soft open file limit
> to the hard open file limit.

Not sure that's quite the right thing to do for postmaster. What I'd start
with is to increase the soft limit to
  "already used files" + max_files_per_process.

That way we still limit "resource" usage, but react better to already used
FDs. If io_uring, listen_addresses, whatnot use FDs
max_files_per_process would be added ontop.

Then we can separately discuss increasing max_files_per_process more
aggressively.


I don't see a downside to just increasing the soft limit for pgbench. It
avoids the stupid cycle of getting "need at least %d open files, but system
limit is %ld", increase ulimit, retry, without any non-theoretical downsides.


> Doing so is especially useful for the AIO work that Andres is doing, because
> io_uring consumes a lot of file descriptors.

Yep.


One more reason this is a good idea is that we'll also need this for
threading, since there all client connections obviously will eat into the
"normal file descriptor" budget.

Greetings,

Andres Freund