From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | David Geier <geidav(dot)pg(at)gmail(dot)com> |
Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Lukas Fittl <lukas(at)fittl(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc? |
Date: | 2023-02-07 18:12:18 |
Message-ID: | 20230207181218.47irz3of34qsww5l@awork3.anarazel.de |
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Lists: | pgsql-hackers |
Hi,
On 2023-01-24 14:30:34 +0100, David Geier wrote:
> Attached is v7 of the patch:
>
> - Rebased on latest master (most importantly on top of the int64 instr_time
> commits). - Includes two commits from Andres which introduce
> INSTR_TIME_SET_SECONDS(), INSTR_TIME_IS_LT() and WIP to report
> pg_test_timing output in nanoseconds. - Converts ticks to nanoseconds only
> with integer math, while accounting for overflow. - Supports RDTSCP via
> INSTR_TIME_SET_CURRENT() and introduced INSTR_TIME_SET_CURRENT_FAST() which
> uses RDTSC.
>
> I haven't gotten to the following:
>
> - Looking through all calls to INSTR_TIME_SET_CURRENT() and check if they
> should be replaced by INSTR_TIME_SET_CURRENT_FAST(). - Reviewing Andres
> commits. Potentially improving on pg_test_timing's output. - Looking at
> enabling RDTSC on more platforms. Is there a minimum set of platforms we
> would like support for? Windows should be easy. That would also allow to
> unify the code a little more. - Add more documentation and do more testing
> around the calls to CPUID. - Profiling and optimizing the code. A quick test
> showed about 10% improvement over master with TIMING ON vs TIMING OFF, when
> using the test-case from Andres' e-mail that started this thread.
>
> I hope I'll find time to work on these points during the next days.
This fails to build on several platforms:
https://cirrus-ci.com/github/postgresql-cfbot/postgresql/commitfest%2F42%2F3751
Greetings,
Andres Freund
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