From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix performance issue in deadlock-parallel isolation test.
Date: Wed, 09 Apr 2025 16:28:40 +0000
Message-ID: <E1u2YI4-003T9A-0h@gemulon.postgresql.org> (raw)
Fix performance issue in deadlock-parallel isolation test.
With debug_discard_caches = 1, the runtime of this test script
increased by about a factor of 10 after commit 0dca5d68d. That's
causing some of our buildfarm animals to fail with a timeout.
The reason for the increased time is that now we are re-planning
some intentionally-non-inlineable SQL functions on every execution,
where the previous coding held onto the original plans throughout
the outer query. The previous behavior was arguably quite buggy,
so I don't think 0dca5d68d deserves blame here. But we would
like this test script to not take so long.
To fix, instead of forcing a "parallel safe" label via a
non-inlineable SQL function, apply it directly to the advisory-lock
functions by making internal-language aliases for them. A small
problem is that the advisory-lock functions return void but this
test would really like them to return integer 1. I cheated here by
declaring the aliases as returning "int". That's perhaps undue
familiarity with the implementation of PG_RETURN_VOID(), but that
hasn't changed in twenty years and is unlikely to do so in the next
twenty. That gets us an integer 0 result, and then an inline-able
wrapper to convert that to an integer 1 allows the rest of the script
to remain unchanged.
For me, this reduces the runtime with debug_discard_caches = 1
by about 100x, making the test comfortably faster than before
instead of slower.
Discussion: https://postgr.es/m/136163.1744179562@sss.pgh.pa.us
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/837cc73af29cd9c63515a6f2a36f54dd703a3a3f
Modified Files
--------------
src/test/isolation/specs/deadlock-parallel.spec | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-committers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix performance issue in deadlock-parallel isolation test.
In-Reply-To: <E1u2YI4-003T9A-0h@gemulon.postgresql.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox