Re: Checkpointer write combining

On Mon, Dec 15, 2025 at 4:36 AM Soumya S Murali
<soumyamurali(dot)work(at)gmail(dot)com> wrote:
>
> With reference to the last patches (v11) I received [1] and while reviewing Melanie’s latest feedback, I understood that PageSetBatchChecksumInplace() is currently WIP and depends on upcoming changes to hint-bit locking. It will be contrary to the flow if I propose new functional changes to checksum batching at this time. So for now I will focus on preparatory or documentation improvements until I get the updates on dependencies.
> Regarding my patch attached, the patch introduces write-combining during checkpoints by batching contiguous buffers and allowing them to be written using vectorized I/O. My patch includes write-combining for checkpoint buffer flushes, contiguous buffer batching, Preserved WAL ordering, locking, and buffer state invariants. The change is currently limited to the checkpointer path (BufferSync()). So far I tested my implementation and found that all the regression (233 tests) and isolation tests (121 tests) got passed, the manual pgbench validation completed successfully and also verified pg_stat_bgwriter counters before and after checkpoints. So far the implementation is stable in my system.

Can you explain how your implementation differs from what was posted
in v11 0006 [1]? That implements checkpointer write combining. I'm
open to ideas for improving the code, but I don't understand how your
patch is supposed to fit into the ongoing work on this thread.

- Melanie

[1] https://www.postgresql.org/message-id/CAAKRu_ZiEpE_EHww3S3-E3iznybdnX8mXSO7Wsuru7%3DP9Y%3DczQ%40mail.gmail.com