Horton

Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

David Geier <geidav.pg@gmail.com>

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From: David Geier <geidav.pg@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, vignesh C <vignesh21@gmail.com>, Lukas Fittl <lukas@fittl.com>, Michael Paquier <michael@paquier.xyz>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, pgsql-hackers@postgresql.org
Date: 2023-01-23T17:52:44Z
Lists: pgsql-hackers

Commits

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  1. pg_test_timing: Also test RDTSC[P] timing, report time source, TSC frequency

  2. Allow retrieving x86 TSC frequency/flags from CPUID

  3. instrumentation: Standardize ticks to nanosecond conversion method

  4. instrumentation: Use Time-Stamp Counter on x86-64 to lower overhead

  5. Zero initialize uses of instr_time about to trigger compiler warnings

  6. instr_time: Represent time as an int64 on all platforms

  7. Add 250c8ee07ed to git-blame-ignore-revs

Hi,

On 1/21/23 06:31, Andres Freund wrote:
> I pushed the int64-ification commits.

Great. I started rebasing.

One thing I was wondering about: why did you chose to use a signed 
instead of an unsigned 64-bit integer for the ticks?
>> If you have time to look at the pg_test_timing part, it'd be
>> appreciated. That's a it larger, and nobody looked at it yet. So I'm a bit
>> hesitant to push it.
> I haven't yet pushed the pg_test_timing (nor it's small prerequisite)
> patch.
>
> I've attached those two patches. Feel free to include them in your series if
> you want, then the CF entry (and thus cfbot) makes sense again...
I'll include them in my new patch set and also have a careful look at them.

-- 
David Geier
(ServiceNow)