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Re: Better shared data structure management and resizable shared data structures

Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>

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From: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, chaturvedipalak1911@gmail.com
Date: 2026-04-05T16:23:43Z
Lists: pgsql-hackers

Attachments

On Sun, Apr 5, 2026 at 7:38 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> On Sun, Apr 5, 2026 at 11:18 AM Ashutosh Bapat
> <ashutosh.bapat.oss@gmail.com> wrote:
> >
> >
> > I will post my resizable shmem structures patch in a separate email in
> > this thread but continue to review your patches.
>
> I reviewed the SLRU patch. This is the first time I am looking at SLRU
> code, so my review may not be sufficient. As far as I understand, the
> patch faithfully copies the functionality from the old system to the
> new system. I didn't find any issues there.
>
> I think calls to SimpleLruRequest() reads much better than SimpleLruInit().
>
> Both MultiXactShmemInit and MultiXactShmemAttach set
> OldestMemberMXactId, OldestVisibleMXactId. In future if we add another
> global variable to point to the shared memory, somebody needs to
> remember to initialize it in both these functions. Maybe deduplicate
> it with something like attached? Similarly for PredicateLock related
> changes.

Sorry, I attached the wrong patch. Here's the right patch.

-- 
Best Wishes,
Ashutosh Bapat

Commits

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

  1. Tidy up #ifdef USE_INJECTION_POINTS guards

  2. Convert all remaining subsystems to use the new shmem allocation API

  3. Convert buffer manager to use the new shmem allocation functions

  4. Add alignment option to ShmemRequestStruct()

  5. Convert AIO to use the new shmem allocation functions

  6. Convert SLRUs to use the new shmem allocation functions

  7. Refactor shmem initialization code in predicate.c

  8. Use the new shmem allocation functions in a few core subsystems

  9. Convert lwlock.c to use the new shmem allocation functions

  10. Introduce a registry of built-in shmem subsystems

  11. Convert pg_stat_statements to use the new shmem allocation functions

  12. Add a test module to test after-startup shmem allocations

  13. Introduce a new mechanism for registering shared memory areas

  14. Move some code from shmem.c and shmem.h

  15. Improve test_lwlock_tranches

  16. Test pg_stat_statements across crash restart

  17. Refactor PredicateLockShmemInit to not reuse var for different things

  18. Refactor ShmemIndex initialization

  19. Add a new shmem_request_hook hook.