Date: Wed, 11 Feb 2026 10:58:41 +0000
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Andres Freund <andres@anarazel.de>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: PGPROC alignment (was Re: pgsql: Separate
 RecoveryConflictReasons from procsignals)
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Hi,

On Wed, Feb 11, 2026 at 12:03:51PM +0200, Heikki Linnakangas wrote:
> On 11/02/2026 06:40, Bertrand Drouvot wrote:
> > > With this, sizeof(PGPROC) == 864 without the explicit alignment to
> > > PG_CACHE_LINE_SIZE, and 896 with it.
> > 
> > I can see 876 -> 896 on my side:
> > 
> > /*    872      |       4 */    uint32 wait_event_info;
> > /* XXX 20-byte padding   */
> > 
> >                                 /* total size (bytes):  896 */
> >                               }
> 
> Interesting. I've attached 'pahole bin/postgres' output from my laptop. It's
> Linux on arm64.

Thanks!

Got it: I was using "-DCACHEDEBUG -DWAL_DEBUG -DLOCK_DEBUG -DDEBUG_DEADLOCK"
so that with LOCK_DEBUG in place then LWLock size is 32 bytes (vs 16 in your case).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com