Re: make LWLockCounter a global variable

On Fri, Aug 29, 2025 at 06:52:48AM +0000, Bertrand Drouvot wrote:
> On Thu, Aug 28, 2025 at 05:56:07PM -0400, Tom Lane wrote:
>> No objection here. As a small improvement, perhaps you could swap
>> around the code in LWLockShmemSize so that the order in which it
>> considers size contributions matches the physical layout, more
>> or less like
>>
>> [...]
>>
>> I find it a little confusing that that code doesn't line up
>> exactly with what CreateLWLocks does.
>
> +1.

Good idea. Here's a new version of the patch. If CI is happy with it,
I'll go ahead and commit it.

> Another option could be to not change CreateLWLocks() at all, except removing the
> local variable:
>
> @@ -423,7 +424,6 @@ CreateLWLocks(void)
> if (!IsUnderPostmaster)
> {
> Size spaceLocks = LWLockShmemSize();
> - int *LWLockCounter;
>
> to use the global variable. That way we preserve the current memory layout and
> there is no need to change LWLockShmemSize().

That would make the patch smaller, but IMHO it kind-of defeats the purpose,
which is to make this stuff simpler and easier to follow.

--
nathan