Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Lukas Fittl <lukas(at)fittl(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, David Geier <geidav(dot)pg(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com>, Tomas Vondra <tomas(at)vondra(dot)me>
Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
Date: 2025-07-29 02:30:11
Message-ID: aIgyM-sdzMs9toYQ@paquier.xyz
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On Mon, Jul 28, 2025 at 03:38:20PM +0900, Michael Paquier wrote:
> On Sun, Jul 27, 2025 at 12:50:54PM -0700, Lukas Fittl wrote:
>> - Fix a typo (configure was incorrectly checking for "__get_cpuidex", vs
>> meson.build was doing it correctly)
>
> It seems to me that this is an independent issue that had better be
> backpatched down to where this configure check has been introduced,
> no?

Please note that updates of ./configure should never be manual, these
are done as follows:
- Update of ./autoconf.ac
- run of autoreconf -i or equivalent to update ./configure. (I just
use the former, just my no-brainer to handle things. Committers are
usually responsible for that, but it may matter to keep the CI happy.)

And I have noticed a second inconsistency with __cpuid(), both
introduced by 3dc2d62d0486 as far as I can see, so we have never
checked for these routines. This is an independent issue for
something that should be backpatched, so I've spawned a new thread
(don't worry you have author credits):
https://www.postgresql.org/message-id/aIgwNYGVt5aRAqTJ@paquier.xyz
--
Michael

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