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base repository: postgresql-cfbot/postgresql
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head repository: postgresql-cfbot/postgresql
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  • 2 commits
  • 3 files changed
  • 2 contributors

Commits on May 29, 2025

  1. Improve accounting for memory used by shared hash tables 

    pg_shmem_allocations tracks the memory allocated by ShmemInitStruct(),
but for shared hash tables that covered only the header and hash
directory.  The remaining parts (segments and buckets) were allocated
later using ShmemAlloc(), which does not update the shmem accounting.
Thus, these allocations were not shown in pg_shmem_allocations.

This commit improves the situation by allocating all the hash table
parts at once, using a single ShmemInitStruct() call. This way the
ShmemIndex entries (and thus pg_shmem_allocations) better reflect the
proper size of the hash table.u

This does not change anything for non-shared hash tables.

This changes the alignment a bit. ShmemAlloc() aligns the chunks using
CACHELINEALIGN(), which means some parts (header, directory, segments)
were aligned this way. Allocating all parts as a single chunk removes
this (implicit) alignment. We've considered adding explicit alignment,
but we've decided not to - it seems to be merely a coincidence due to
using the ShmemAlloc() API, not due to necessity.

Author: Rahila Syed <rahilasyed90@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://postgr.es/m/CAH2L28vHzRankszhqz7deXURxKncxfirnuW68zD7+hVAqaS5GQ@mail.gmail.com
    @Rahila
    Rahila authored and Commitfest Bot committed May 29, 2025
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  2. [CF 5620] v10 - Improve monitoring of shared memory allocations 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5620

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAH2L28vgzvTUqNwQay=jx4w30sHMx_pC+emnZErv8oX0R+SALQ@mail.gmail.com
Author(s): Rahila Syed
    Commitfest Bot committed May 29, 2025
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