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help / color / mirror / Atom feedFrom: Jakub Wartak <[email protected]>
To: Lukas Fittl <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Hannu Krosing <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Pavel Stehule <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Ibrar Ahmed <[email protected]>
Cc: Maciek Sakrejda <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: David Geier <[email protected]>
Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
Date: Wed, 25 Feb 2026 12:57:19 +0100
Message-ID: <CAKZiRmwWKBzLmCjiENVOS8FijDsoOyCh29YwSiZcak61oM77DA@mail.gmail.com> (raw)
In-Reply-To: <CAP53Pkx1bK1FB71_nBqYmzvSSXnp_MbE0ZDnU+baPJF6Ud2WDA@mail.gmail.com>
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On Wed, Feb 25, 2026 at 11:01 AM Lukas Fittl <[email protected]> wrote:
[..]
> See attached v9, rebased, with feedback addressed, unless otherwise noted.
FWIW, I've tried this on FreeBSD and I couldn't understand why I
couldn't enable TSC
(atlought) the cpuid tools reported RDTSCP being available. I have found out
that set_tsc_frequency_khz() returns false and tsc_frequency_khz==0 before even
inquiry for is_rdtscp_available() is done. As this was on virtualbox VM (so not
suppoprted by current code), I think this is pretty clear we'll need some way of
informing users why he cannot SET timing_clock_source to TSC. Possibly errhint()
could differentiate the reason? E.g.
"failed to auto-detect TSC frequency (potential hypervisor issue)" or
"CPU RDTSCP instructions are not available"
-J.
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Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
In-Reply-To: <CAKZiRmwWKBzLmCjiENVOS8FijDsoOyCh29YwSiZcak61oM77DA@mail.gmail.com>
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