Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

Lukas Fittl <lukas@fittl.com>

From: Lukas Fittl <lukas@fittl.com>

To: 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>, David Geier <geidav.pg@gmail.com>

Date: 2026-03-26T01:17:44Z

Lists: pgsql-hackers

Attachments

v14-0005-pg_test_timing-Also-test-RDTSC-RDTSCP-timing-and.patch (application/octet-stream) patch v14-0005
v14-0004-instrumentation-Use-Time-Stamp-Counter-TSC-on-x8.patch (application/octet-stream) patch v14-0004
v14-0002-pg_test_timing-Reduce-per-loop-overhead.patch (application/octet-stream) patch v14-0002
v14-0001-Check-for-HAVE__CPUIDEX-and-HAVE__GET_CPUID_COUN.patch (application/octet-stream) patch v14-0001
v14-0003-instrumentation-Streamline-ticks-to-nanosecond-c.patch (application/octet-stream) patch v14-0003
v14-0006-instrumentation-ARM-support-for-fast-time-measur.patch (application/octet-stream) patch v14-0006

Hi John,

On Tue, Mar 24, 2026 at 10:39 PM John Naylor <johncnaylorls@gmail.com> wrote:
> Okay, pushed that way. I also took the liberty of moving a couple
> comment changes in 0005 to here. My hope is that will reduce merge
> conflicts with the AVX checksums patch, since that one also
> invalidates one of those comments and it's not clear which will be
> committed first.

Great, thank you!

Attached rebased v14 - no changes otherwise.

Thanks,
Lukas

-- 
Lukas Fittl

Commits

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

pg_test_timing: Show additional TSC clock source debug info
- 5ba34f6dc838 19 (unreleased) landed
instrumentation: Avoid CPUID 0x15/0x16 for Hypervisor TSC frequency
- 7fc36c5db550 19 (unreleased) landed
pg_test_timing: Also test RDTSC[P] timing, report time source, TSC frequency
- 16fca4825483 19 (unreleased) landed
Allow retrieving x86 TSC frequency/flags from CPUID
- bcb2cf41f964 19 (unreleased) landed
instrumentation: Standardize ticks to nanosecond conversion method
- 0022622c93d9 19 (unreleased) landed
instrumentation: Use Time-Stamp Counter on x86-64 to lower overhead
- 294520c44487 19 (unreleased) landed
Check for __cpuidex and __get_cpuid_count separately
- effaa464afd3 19 (unreleased) landed
pg_test_timing: Reduce per-loop overhead
- 82c0cb4e672d 19 (unreleased) landed
Refactor handling of x86 CPUID instructions
- be6a7494d2e3 19 (unreleased) landed
instrumentation: Drop INSTR_TIME_SET_CURRENT_LAZY macro
- 9d6294c09ed0 19 (unreleased) landed
Rename pg_crc32c_sse42_choose.c for general purpose
- b9278871f991 19 (unreleased) cited
Zero initialize uses of instr_time about to trigger compiler warnings
- 25b2aba0c3a5 16.0 landed
instr_time: Represent time as an int64 on all platforms
- 03023a2664f8 16.0 landed
Add 250c8ee07ed to git-blame-ignore-revs
- ff23b592ad66 16.0 cited