Feedback-ID: id4a34324:Fastmail
Date: Thu, 8 Jun 2023 11:48:48 -0700
From: Andres Freund <andres@anarazel.de>
To: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: Hannu Krosing <hannuk@google.com>, Robert Haas <robertmhaas@gmail.com>,
	"Jonathan S. Katz" <jkatz@postgresql.org>,
	Heikki Linnakangas <hlinnaka@iki.fi>, Tom Lane <tgl@sss.pgh.pa.us>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Let's make PostgreSQL multi-threaded
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Hi,

On 2023-06-08 17:55:57 +0200, Matthias van de Meent wrote:
> While I agree that "sharing page tables across processes" is useful,
> it looks like it'd be much more effort to correctly implement for e.g.
> DSM than implementing threading.
> Konstantin's diff is "only" 20.1k lines [0] added and/or modified,
> which is a lot, but it's manageable (13k+ of which are from files that
> were auto-generated and then committed, likely accidentally).

Honestly, I don't think this patch is in a good enough state to allow a
realistic estimation of the overall work. Making global variables TLS is the
*easy* part.  Redesigning postmaster, definining how to deal with extension
libraries, extension compatibility, developing tools to make developing a
threaded postgres feasible, dealing with freeing session lifetime memory
allocations that previously were freed via process exit, making the change
realistically reviewable, portability are all much harder.

Greetings,

Andres Freund