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base repository: postgresql-cfbot/postgresql
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  • 4 commits
  • 11 files changed
  • 2 contributors

Commits on Aug 31, 2025

  1. Use consistent naming of the clock-sweep algorithm. 

    Minor edits to comments only.
    @gburd
    gburd authored and Commitfest Bot committed Aug 31, 2025
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  2. Eliminate the freelist from the buffer manager and depend on clock-sweep 

    This set of changes removes the list of available buffers and instead
simply uses the clock-sweep algorithm to find and return an available
buffer.  While on the surface this appears to be removing an
optimization it is in fact eliminating code that induces overhead in the
form of synchronization that is problemmatic for multi-core systems.
This also removes the have_free_buffer() function and simply caps the
pg_autoprewarm process to at most NBuffers.
    @gburd
    gburd authored and Commitfest Bot committed Aug 31, 2025
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  3. Track buffer usage per-backend and use that to inform buffer managment 

    Implement a comprehensive buffer pressure monitoring and management system
to improve PostgreSQL's buffer replacement efficiency under high load.

Problems:
- Buffer pressure was only detectable reactively during allocation failures
- No visibility into which backends contribute most to buffer contention
- High usage counts force multiple clock-sweep passes under heavy load
- bgwriter had limited intelligence about system-wide buffer usage patterns

Solution:
- Add per-backend buffer usage counters
- Implement proactive buffer pressure calculation in bgwriter
- Add targeted buffer writing for high-usage backends (90th percentile)
- Adjust rate of usage count reduction when pressure exceeds 75% threshold

Benefits:
- Reduces buffer allocation stalls by proactively managing pressure
- Provides fair resource management by targeting high-usage backends
- Improves system responsiveness under memory pressure
- Maintains backward compatibility with existing buffer management
- Enables better observability of buffer usage patterns per backend
    @gburd
    gburd authored and Commitfest Bot committed Aug 31, 2025
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  4. [CF 5928] v14 - Remove freelist and the buffer_strategy_lock 

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

https://commitfest.postgresql.org/patch/5928

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/[email protected]
Author(s): Greg Burd
    Commitfest Bot committed Aug 31, 2025
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