Re: Fix pg_stat_get_backend_wait_event() for aux processes

On 04/02/2026 10:02, Bertrand Drouvot wrote:
> On Tue, Feb 03, 2026 at 10:29:27PM +0200, Heikki Linnakangas wrote:
>> There might be a performance argument too,
>
> yeah, not sure but with the patch in place the size of PGPROC goes from
> 832 bytes to 824 bytes. Is it worth to add extra padding so that it still remain
> a multiple of 64?

Hmm, I don't think so. We've never given cacheline alignment any thought
when we've changed the PGPROC fields in the past (or at least I
haven't). Perhaps we should, but it would warrant a separate investigation.

Now that I look at that, the most frequently accessed fields are not at
the beginning or end of the struct, so I don't think there's much harm
in sharing cache lines. And the really hot GetSnapshotData() function
uses the "mirrored" arrays anyway.

- Heikki