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Date: Mon, 23 Feb 2026 17:13:29 +0100
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Subject: Re: PGPROC alignment (was Re: pgsql: Separate RecoveryConflictReasons
 from procsignals)
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
 Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Andres Freund <andres@anarazel.de>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
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From: Peter Eisentraut <peter@eisentraut.org>
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On 13.02.26 09:03, Bertrand Drouvot wrote:
> +/*
> + * If compiler understands aligned pragma, use it to align the struct at cache
> + * line boundaries.  This is just for performance, to (a) avoid false sharing
> + * and (b) to make the multiplication / division to convert between PGPROC *
> + * and ProcNumber be a little cheaper.
> + */
> +#if defined(pg_attribute_aligned)
> +                       pg_attribute_aligned(PG_CACHE_LINE_SIZE)
> +#endif
> +PGPROC;

You can/should use C11 standard alignas(), so you don't need to worry 
about whether it's supported or not.