Message-ID: <a6159474-a06b-4874-9e4f-f06516995860@iki.fi>
Date: Tue, 10 Feb 2026 17:52:16 +0200
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Subject: Re: pgsql: Separate RecoveryConflictReasons from procsignals
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: pgsql-committers@lists.postgresql.org
References: <E1vpon6-002LVp-2z@gemulon.postgresql.org>
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From: Heikki Linnakangas <hlinnaka@iki.fi>
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On 10/02/2026 17:19, Bertrand Drouvot wrote:
> Hi,
> 
> On Tue, Feb 10, 2026 at 02:32:37PM +0000, Heikki Linnakangas wrote:
>> Separate RecoveryConflictReasons from procsignals
>>
>> Share the same PROCSIG_RECOVERY_CONFLICT flag for all recovery
>> conflict reasons. To distinguish, have a bitmask in PGPROC to indicate
>> the reason(s).
> 
> I did not look at the thread, so sorry to be late, but that makes the size of PGPROC
> going from 832 to 840 bytes, so not a multiple of 64 anymore. Is that something
> to worry about? (same kind of discussion in [1]).
> 
> [1]: https://postgr.es/m/tw53roer2j4quxh7vlyv62drc5fo6c6zdltvl6d2dttqa62uhi%40stwlpdwlftpj

Right, that's a fair question. I hope the cache line alignment is not 
critical for performance, because the alignment is completely accidental 
today. I checked the size on different versions:

master:  840 (after this commit)
v18:     832
v17:     888
v14-v16: 880

So v18 was the outlier in that it happened to be 64-byte aligned.

If there's a performance reason to keep have it be aligned - and maybe 
there is - we should pad it explicitly.

- Heikki