From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, x4mmm@yandex-team.ru,
        dilipbalaut@gmail.com, tndrwang@gmail.com,
        pgsql-hackers@lists.postgresql.org, tomas.vondra@enterprisedb.com
Subject: Re: SLRU optimization - configurable buffer pool and partitioning the
 SLRU lock
In-reply-to: <202403031358.b435eh7u72td@alvherre.pgsql>
References: <202403031358.b435eh7u72td@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@alvh.no-ip.org>
	message dated "Sun, 03 Mar 2024 14:58:39 +0100"
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Date: Mon, 04 Mar 2024 17:14:32 -0500
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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: '!=3D': '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: '!=3D': 'SlruPageStatus *' differs in levels =
of indirection from 'int'

These lines are

	Assert(&shared->page_status[slotno] !=3D SLRU_PAGE_EMPTY);

	Assert(&ctl->shared->page_status[slotno] !=3D 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 !=3D NULL".  But that
doesn't look like a useful test to be making.

			regards, tom lane