Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

From: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
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>, Michael Paquier <michael(at)paquier(dot)xyz>, 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: 2025-10-19 18:16:20
Message-ID: 202510191732.kxjptludow3i@alvherre.pgsql
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On 2025-Jul-27, Lukas Fittl wrote:

> See attached v11 (and moved to the PG19-2 commitfest), split into a new set
> of patches:

I rebased (but not reviewed) this patchset now that Michael committed
part of 0001, as seen in another thread.

Quickly looking at 0003, I wonder if adding a separate --fast switch to
pg_test_timing is really what we want. Why not report both the fast and
legacy measurements in platforms that support both, instead? If I were
a consultant trying to understand a customer's system, I would have to
ask them to run it twice just in case 'fast' is supported, and I don't
think that's very helpful. Also, were the doc updates lost somehow, or
were they made irrelevant by other concurrent pg_test_timing
development?

Thanks

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"Ninguna manada de bestias tiene una voz tan horrible como la humana" (Orual)

Attachment Content-Type Size
v12-0001-cpuidex-check-Support-detecting-newer-GCC-versio.patch text/x-diff 2.2 KB
v12-0002-Use-time-stamp-counter-to-measure-time-on-Linux-.patch text/x-diff 17.2 KB
v12-0003-pg_test_timing-Add-fast-flag-to-test-fast-timing.patch text/x-diff 7.5 KB

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