Horton

Re: Buffer locking is special (hints, checksums, AIO writes)

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Noah Misch <noah@leadboat.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org, Melanie Plageman <melanieplageman@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2025-09-01T02:03:55Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Require share-exclusive lock to set hint bits and to flush

  2. lwlock: Remove ForEachLWLockHeldByMe

  3. bufmgr: Implement buffer content locks independently of lwlocks

  4. bufmgr: Change BufferDesc.state to be a 64-bit atomic

  5. heapam: Add batch mode mvcc check and use it in page mode

  6. freespace: Don't modify page without any lock

  7. heapam: Move logic to handle HEAP_MOVED into a helper function

  8. bufmgr: Optimize & harmonize LockBufHdr(), LWLockWaitListLock()

  9. bufmgr: Add one-entry cache for private refcount

  10. bufmgr: Separate keys for private refcount infrastructure

  11. Add pg_atomic_unlocked_write_u64

  12. Rename BUFFERPIN wait event class to BUFFER

  13. bufmgr: Turn BUFFER_LOCK_* into an enum

  14. lwlock: Fix, currently harmless, bug in LWLockWakeup()

  15. bufmgr: Use atomic sub for unpinning buffers

  16. bufmgr: Allow some buffer state modifications while holding header lock

  17. bufmgr: Fix valgrind checking for buffers pinned in StrategyGetBuffer()

  18. bufmgr: Don't lock buffer header in StrategyGetBuffer()

  19. bufmgr: fewer calls to BufferDescriptorGetContentLock

  20. bufmgr: Fix signedness of mask variable in BufferSync()

  21. bufmgr: Introduce FlushUnlockedBuffer

  22. Improve ReadRecentBuffer() scalability

On Wed, Aug 27, 2025 at 10:03:08AM -0400, Robert Haas wrote:
> If we were to use the existing PostgreSQL naming convention, I think
> I'd probably argue that the nearest parallel to this level is
> ShareUpdateExclusive: a self-exclusive lock level that permits
> ordinary table access to continue while blocking exclusive locks, used
> for an in-flight maintenance operation. But that's arguable, of
> course.

ShareUpdateExclusive is a term that's been used for some time now and
relates to knowledge that's quite spread in the tree, so it feels like
a natural fit for the use-case described on this thread as we'd want a
self-conflicting lock.  share-exclusive did not sound that bad to me,
TBH, quite the contrary, when applied to buffer locking for aio.

"intent" is also a word I've bumped quite a lot into while looking at
some naming convention, but this is more related to the fact that a
lock is going to be taken, which we don't really have.  So that feels
off.
--
Michael