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

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>

To: Andrey Borodin <x4mmm@yandex-team.ru>

Cc: Hannu Krosing <hannuk@google.com>, Peter Eisentraut <peter@eisentraut.org>, pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2025-07-08T19:29:48Z

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 →

Force LC_NUMERIC to C while running TAP tests.
- f25792c541e5 19 (unreleased) landed
Minor tweaks for pg_test_timing.
- 9dcc7641444f 19 (unreleased) landed
Change pg_test_timing to measure in nanoseconds not microseconds.
- 0b096e379e6f 19 (unreleased) landed

Andrey Borodin <x4mmm@yandex-team.ru> writes:
>> On 8 Jul 2025, at 23:07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The fact that the clock tick is about 40ns is extremely 
>> obvious in this presentation.

> FWIW while working on UUID v7 Masahiko found that if we try to read real time with clock_gettime(CLOCK_REALTIME,) measurement is truncated to microseconds.

Yeah.  Bear in mind that instr_time.h uses CLOCK_MONOTONIC_RAW on
macOS, so that's what we're looking at here.

			regards, tom lane