Re: First draft of PG 17 release notes - Mailing list pgsql-hackers

On Fri, May 10, 2024 at 7:20 PM Bruce Momjian <bruce@momjian.us> wrote:
>
> > Thanks a lot for this work Bruce! It looks like commit
> > https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=91f2cae7a4e664e9c0472b364c7db29d755ab151
> > is missing from daft release notes. Just curious to know if it's
> > intentional or a miss out.
>
> I did not mention it because the commit didn't mention any performance
> benefit and it seemed more like an internal change than something people
> needed to know about.

Yes, it's an internal feature for someone not using Direct IO for WAL
and helps achieve things mentioned at

https://www.postgresql.org/message-id/flat/20230125211540.zylu74dj2uuh3k7w%40awork3.anarazel.de#0cac0a0d219129e32329831adea05db5
(I'm hoping to target them for PG18). It starts to show visible
benefits if someone enables direct IO for WAL (for whatever reasons)
https://www.postgresql.org/message-id/CALj2ACV6rS%2B7iZx5%2BoAvyXJaN4AG-djAQeM1mrM%3DYSDkVrUs7g%40mail.gmail.com
and https://www.postgresql.org/message-id/20230127061745.46yu4ksitzociwkt%40awork3.anarazel.de.

I'm okay if 91f2cae7 is left out for the reason that Direct IO for WAL
isn't something used in production and debug_io_direct is a developer
option.

> I could reword and merge it into this item, if
> you think I should:
>
>          Improve performance of heavily-contended WAL writes (Bharath Rupireddy)

I think both the commits are for different purposes - one is for WAL
wrties, another is for WAL reads.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com