Horton
Menu

Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

David Geier <geidav.pg@gmail.com>

View thread
From: David Geier <geidav.pg@gmail.com>
To: Lukas Fittl <lukas@fittl.com>, John Naylor <johncnaylorls@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Jakub Wartak <jakub.wartak@enterprisedb.com>, Hannu Krosing <hannuk@google.com>, Robert Haas <robertmhaas@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>, vignesh C <vignesh21@gmail.com>, Michael Paquier <michael@paquier.xyz>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2026-03-23T08:00:34Z
Lists: pgsql-hackers 
Hi Lukas!

Thanks for pushing this forward.

On 22.03.2026 19:13, Lukas Fittl wrote:

> TSC calibration improvements:
> - Pass TSC frequency to child processes for EXEC_BACKEND, this makes
> TSC calibration usable on Windows, per off-list suggestion from Andres
> - To support the EXEC_BACKEND change, refactor tsc_frequency_khz to
> have a sentinel value of -1 indicating the TSC was not initialized, vs
> 0 indicating it was initialized but isn't usable, and drop
> has_usable_tsc variable

Have you tested the latest patch set on Windows? Let me know if you want
me to do that.

--
David Geier

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pg_test_timing: Show additional TSC clock source debug info

  2. instrumentation: Avoid CPUID 0x15/0x16 for Hypervisor TSC frequency

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

  4. Allow retrieving x86 TSC frequency/flags from CPUID

  5. instrumentation: Standardize ticks to nanosecond conversion method

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

  7. Check for __cpuidex and __get_cpuid_count separately

  8. pg_test_timing: Reduce per-loop overhead

  9. Refactor handling of x86 CPUID instructions

  10. instrumentation: Drop INSTR_TIME_SET_CURRENT_LAZY macro

  11. Rename pg_crc32c_sse42_choose.c for general purpose

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

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

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