Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

Pavel Stehule <pavel.stehule@gmail.com>

From: Pavel Stehule <pavel.stehule@gmail.com>

To: Tomas Vondra <tomas.vondra@enterprisedb.com>

Cc: David Geier <geidav.pg@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>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2023-01-16T20:39:04Z

Lists: pgsql-hackers

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: 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
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

po 16. 1. 2023 v 21:34 odesílatel Tomas Vondra <
tomas.vondra@enterprisedb.com> napsal:

> Hi,
>
> there's minor bitrot in the Mkvcbuild.pm change, making cfbot unhappy.
>
> As for the patch, I don't have much comments. I'm wondering if it'd be
> useful to indicate which timing source was actually used for EXPLAIN
> ANALYZE, say something like:
>
>  Planning time: 0.197 ms
>  Execution time: 0.225 ms
>  Timing source: clock_gettime (or tsc)
>
> There has been a proposal to expose this as a GUC (or perhaps as explain
> option), to allow users to pick what timing source to use. I wouldn't go
> that far - AFAICS is this is meant to be universally better when
> available. But knowing which source was used seems useful.
>

+1

Pavel


>
> regards
>
> --
> Tomas Vondra
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>
>
>