From: Tom Lane <tgl@sss.pgh.pa.us>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Cc: dipiets@amazon.com
Subject: Re: use a non-locking initial test in TAS_SPIN on AArch64
Date: Wed, 08 Jan 2025 18:07:44 -0500
Message-ID: <1759000.1736377664@sss.pgh.pa.us> (raw)
In-Reply-To: <Z371r_AVOU0WCrBr@nathan>
References: <ZxgDEb_VpWyNZKB_@nathan>
<Z37AA6-SsJoLaifa@nathan>
<tdex7aj3zrvdu22dfgtljbrybrjezbjpr374otnadi6qxywkmc@rzxtb2fbubpy>
<Z371r_AVOU0WCrBr@nathan>
Nathan Bossart <nathandbossart@gmail.com> writes:
> AFAICT TAS_SPIN() is only used for s_lock(), which doesn't appear to be
> used by LWLocks. But I did retry my test from upthread without
> pg_stat_statements and was surprised to find a reproducible 4-6%
> regression.
On what hardware?
I just spent an hour beating on my M4 Pro (the 14-core variant)
and could not detect any outside-the-noise effect of this patch,
with or without pg_stat_statements loaded. There does seem to be
a small fraction-of-a-percent-ish benefit. But the run-to-run
variation with 60-second "pgbench -S" tests is a couple of percent,
so I can't say that that's real.
I do feel pretty sure that the patch doesn't hurt on this
class of hardware.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, nathandbossart@gmail.com, andres@anarazel.de, dipiets@amazon.com
Subject: Re: use a non-locking initial test in TAS_SPIN on AArch64
In-Reply-To: <1759000.1736377664@sss.pgh.pa.us>
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