Feedback-ID: i0fe9450f:Fastmail
Date: Wed, 20 Nov 2024 09:01:26 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Nazir Bilal Yavuz <byavuz81@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: per backend I/O statistics
Message-ID: <Zz0m1k03k5LA_c8S@paquier.xyz>
References: <ZypXy3fH/EyALaTR@ip-10-97-1-34.eu-west-3.compute.internal>
 <Zyqsm6ilLLADAGw2@paquier.xyz>
 <Zyt0Rh6Uwvf+mlA1@ip-10-97-1-34.eu-west-3.compute.internal>
 <ZywO84-2K8fxEIx8@paquier.xyz>
 <ZyzrrFNvXC2YvcNE@ip-10-97-1-34.eu-west-3.compute.internal>
 <Zy4bmvgHqGjcK1pI@ip-10-97-1-34.eu-west-3.compute.internal>
 <ZzWZV9LdyZ9aFSWs@paquier.xyz>
 <ZzX7Y5i56UrOtlRC@ip-10-97-1-34.eu-west-3.compute.internal>
 <ZzvuScIJW9kwnuyE@paquier.xyz>
 <Zzy8x7fGkWEKB7SF@ip-10-97-1-34.eu-west-3.compute.internal>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="Budt3GbHcMlMO0qC"
Content-Disposition: inline
In-Reply-To: <Zzy8x7fGkWEKB7SF@ip-10-97-1-34.eu-west-3.compute.internal>
Archived-At: <https://www.postgresql.org/message-id/Zz0m1k03k5LA_c8S%40paquier.xyz>
Precedence: bulk


--Budt3GbHcMlMO0qC
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Tue, Nov 19, 2024 at 04:28:55PM +0000, Bertrand Drouvot wrote:
> So, for the startup process only, what about?
>=20
> - don't call pgstat_create_backend_stat() in pgstat_beinit()...
> - but call it in StartupXLOG() instead (after the stats are discarded or =
restored).
>=20
> That way we could get rid of the changes linked to the assertion and stil=
l handle
> the startup process particular case. Thoughts?

Hmm.  That may prove to be a good idea in the long-term.  The startup
process is a specific path kicked in at a very early stage, so it is
also a bit weird that we'd try to insert statistics while we are going
to reset them anyway a bit later.  That may also be relevant for
custom statistics, actually, especially if some calls happen in some
hook paths taken before the reset is done.  This could happen for
injection point stats when loading it with shared_preload_libraries,=20
actually, if you load, attach or run a callback at this early stage.
The existing sanity checks are a safety net that we should not change
or adapt for specific stats kinds conditions, IMO.  Perhaps this had
better be done as a patch of its own, on top of the rest.

> Yeah that's the reason why I suggested "pgstat_backend.c". I would not be
> surprised if we add more "per backend" stats (that are not I/O related) i=
n the
> future as the main machinery would be there.

Okay.
--
Michael

--Budt3GbHcMlMO0qC
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=m5en
-----END PGP SIGNATURE-----

--Budt3GbHcMlMO0qC--