Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> Pushed that way, but we can discuss further wording improvements/changes
> if someone wants to propose any.

I just noticed that drongo is complaining about two lines added
by commit 53c2a97a9:

 drongo        | 2024-03-04 14:34:52 | ../pgsql/src/backend/access/transam/slru.c(436): warning C4047: '!=':
'SlruPageStatus*' differs in levels of indirection from 'int' 
 drongo        | 2024-03-04 14:34:52 | ../pgsql/src/backend/access/transam/slru.c(717): warning C4047: '!=':
'SlruPageStatus*' differs in levels of indirection from 'int' 

These lines are

    Assert(&shared->page_status[slotno] != SLRU_PAGE_EMPTY);

    Assert(&ctl->shared->page_status[slotno] != SLRU_PAGE_EMPTY);

These are comparing the address of something with an enum value,
which surely cannot be sane.  Is the "&" operator incorrect?

It looks like SLRU_PAGE_EMPTY has (by chance, or deliberately)
the numeric value of zero, so I guess the majority of our BF
animals are understanding this as "address != NULL".  But that
doesn't look like a useful test to be making.

            regards, tom lane