Horton

Re: optimize atomic exchanges

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Date: 2023-12-01T03:18:15Z
Lists: pgsql-hackers 
On Wed, Nov 29, 2023 at 03:29:05PM -0600, Nathan Bossart wrote:
> I haven't done any sort of performance testing on this yet.  Some
> preliminary web searches suggest that there is unlikely to be much
> difference between cmpxchg and xchg, but presumably there's some difference
> between xchg and doing cmpxchg in a while loop (as is done in
> atomics/generic.h today).  I'll report back once I've had a chance to do
> some testing...

Some rudimentary tests show a >40% speedup with this patch on x86_64.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. Optimize pg_atomic_exchange_u32 and pg_atomic_exchange_u64.