Re: AIO v2.0 - Mailing list pgsql-hackers

From Andres Freund
Subject Re: AIO v2.0
Date
Msg-id s2suzn6rppv7hxxayvlk2wvxlwqa4slzzrxlw5kx7j44txhe7r@4lbgr6aanyp2
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In response to Re: AIO v2.0  (Jelte Fennema-Nio <postgres@jeltef.nl>)
List pgsql-hackers
Hi,

On 2024-12-20 18:27:13 +0100, Jelte Fennema-Nio wrote:
> On Fri, 20 Dec 2024 at 01:54, Andres Freund <andres@anarazel.de> wrote:
> > Arguably the configuration *did* tell us, by having a higher hard limit...
> > <snip>
> > But opting into a higher rlimit, while obviously adhering to the hard limit
> > and perhaps some other config knob, seems fine?
> 
> Yes, totally fine. That's exactly the reasoning why the hard limit is
> so much larger than the soft limit by default on systems with systemd:
> 
> https://0pointer.net/blog/file-descriptor-limits.html

Good link.

This isn't just relevant for using io_uring:

There obviously are several people working on threaded postgres. Even if we
didn't duplicate fd.c file descriptors between threads (we probably will, at
least initially), the client connection FDs alone will mean that we have a lot
more FDs open. Due to the select() issue the soft limit won't be increased
beyond 1024, requiring everyone to add a 'ulimit -n $somehighnumber' before
starting postgres on linux doesn't help anyone.

Greetings,

Andres Freund



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