Re: max_locks_per_transaction v18

thanks for you clarification about additional memory calculations: for
10k connections , 5625kB maybe fine. I justed looked through the
discussions about memory allocation "
https://www.postgresql.org/message-id/cba2406a-66bb-41ac-b1cf-bb898596e0e1%40vondra.me",
I feel confused about the statement "the memory 1000 connections 80MB
there"

Thanks,

James
David Rowley <dgrowleyml(at)gmail(dot)com> 於 2025年8月18日週一 下午2:58寫道：

> On Mon, 18 Aug 2025 at 18:23, James Pang <jamespang886(at)gmail(dot)com> wrote:
> > not tested and any regression found either, with 10k connections,
> and "max_locks_per_transaction=128", it need about more than 1GB extra
> memory,right? per my understanding, max_locks_per_transaction is the max
> locked objects in a transaction (that's not an average locked objects at
> the same time among all connections), but for past-path-lock slots, the
> memory will be allocated based on this parameter after client connection
> established, right? so, even no so many fast lock slots needed, for 10k
> connections, extra memory got allocated there. We may test that in our
> environment, and update then if anything found.
>
> Can you share how you came to 1GB extra?
>
> By my calculations, I believe it's an extra 5625 kB total for the
> entire instance.
>
> select pg_size_pretty((max_locks_per_xact / 16 * 8 +
> max_locks_per_xact / 16 * 4 * 16) * connections::numeric) from
> (values(128,10000)) v(max_locks_per_xact, connections);
>
> David
>