Feedback-ID: id4a34324:Fastmail
Date: Wed, 6 Jul 2022 17:04:46 -0700
From: Andres Freund <andres@anarazel.de>
To: Nitin Jadhav <nitinjadhavpostgres@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
	Ashutosh Sharma <ashu.coek88@gmail.com>,
	Julien Rouhaud <rjuju123@gmail.com>,
	Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>,
	Magnus Hagander <magnus@hagander.net>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Report checkpoint progress with pg_stat_progress_checkpoint
 (was: Report checkpoint progress in server logs)
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Hi,

On 2022-06-13 19:08:35 +0530, Nitin Jadhav wrote:
> > Have you measured the performance effects of this? On fast storage with large
> > shared_buffers I've seen these loops in profiles. It's probably fine, but it'd
> > be good to verify that.
> 
> To understand the performance effects of the above, I have taken the
> average of five checkpoints with the patch and without the patch in my
> environment. Here are the results.
> With patch: 269.65 s
> Without patch: 269.60 s

Those look like timed checkpoints - if the checkpoints are sleeping a
part of the time, you're not going to see any potential overhead.

To see whether this has an effect you'd have to make sure there's a
certain number of dirty buffers (e.g. by doing CREATE TABLE AS
some_query) and then do a manual checkpoint and time how long that
times.

Greetings,

Andres Freund