Horton

Re: What is a typical precision of gettimeofday()?

Andrey Borodin <x4mmm@yandex-team.ru>

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From: "Andrey M. Borodin" <x4mmm@yandex-team.ru>
To: Peter Eisentraut <peter@eisentraut.org>, Hannu Krosing <hannuk@google.com>, Ants Aasma <ants@cybertec.at>, gregsmithpgsql@gmail.com
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2024-06-18T05:47:52Z
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 →

  1. Force LC_NUMERIC to C while running TAP tests.

  2. Minor tweaks for pg_test_timing.

  3. Change pg_test_timing to measure in nanoseconds not microseconds.


> On 19 Mar 2024, at 13:28, Peter Eisentraut <peter@eisentraut.org> wrote:
> 
> I feel that we don't actually have any information about this portability concern.  Does anyone know what precision we can expect from gettimeofday()?  Can we expect the full microsecond precision usually?

At PGConf.dev Hannu Krossing draw attention to pg_test_timing module. I’ve tried this module(slightly modified to measure nanoseconds) on some systems, and everywhere I found ~100ns resolution (95% of ticks fall into 64ns and 128ns buckets).

I’ll add cc Hannu, and also pg_test_timing module authors Ants ang Greg. Maybe they can add some context.


Best regards, Andrey Borodin.