Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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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
Date: 2024-03-04T22:41:58Z
Lists: pgsql-hackers 
I wrote:
> 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.

In hopes of noticing whether there are other similar thinkos,
I permuted the order of the SlruPageStatus enum values, and
now I get the expected warnings from gcc:

In file included from ../../../../src/include/postgres.h:45,
                 from slru.c:59:
slru.c: In function ‘SimpleLruWaitIO’:
slru.c:436:38: warning: comparison between pointer and integer
  Assert(&shared->page_status[slotno] != SLRU_PAGE_EMPTY);
                                      ^~
../../../../src/include/c.h:862:9: note: in definition of macro ‘Assert’
   if (!(condition)) \
         ^~~~~~~~~
slru.c: In function ‘SimpleLruWritePage’:
slru.c:717:43: warning: comparison between pointer and integer
  Assert(&ctl->shared->page_status[slotno] != SLRU_PAGE_EMPTY);
                                           ^~
../../../../src/include/c.h:862:9: note: in definition of macro ‘Assert’
   if (!(condition)) \
         ^~~~~~~~~

So it looks like it's just these two places.

			regards, tom lane

Commits

  1. Fix zeroing of pg_serial page without SLRU bank lock

  2. Fix misspelled assertions

  3. GUC table: Add description to computed variables

  4. Improve performance of subsystems on top of SLRU

  5. Rename SLRU elements in view pg_stat_slru

  6. Use atomic access for SlruShared->latest_page_number

  7. Split use of SerialSLRULock, creating SerialControlLock

  8. Index SLRUs by 64-bit integers rather than by 32-bit integers

  9. Add a macro templatized hashtable.