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GetVictimBuffer() implemented a loop to optimistically lock a clean victim buffer using a goto. Future commits will add batch flushing functionality to GetVictimBuffer. The new logic works better with standard for loop flow control. This commit is only a refactor and does not introduce any new functionality. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/2FA0BAC7-5413-4ABD-94CA-4398FE77750D%40gmail.com Discussion: https://postgr.es/m/flat/CAAKRu_Yjn4mvN9NBxtmsCQSGwup45CoA4e05nhR7ADP-v0WCig%40mail.gmail.com

Before adding write combining to write a batch of blocks when flushing dirty buffers, refactor FlushBuffer() into the preparatory step and actual buffer flushing step. This separation procides symmetry with future code for batch flushing which necessarily separates these steps, as it must prepare multiple buffers before flushing them together. These steps are moved into a new FlushBuffer() helper function, CleanVictimBuffer() which will contain both the batch flushing and single flush code in future commits. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Discussion: https://postgr.es/m/2FA0BAC7-5413-4ABD-94CA-4398FE77750D%40gmail.com Discussion: https://postgr.es/m/flat/CAAKRu_Yjn4mvN9NBxtmsCQSGwup45CoA4e05nhR7ADP-v0WCig%40mail.gmail.com

Operations using BAS_BULKWRITE (COPY FROM and createdb) will inevitably need to flush buffers in the strategy ring in order to reuse them. By eagerly flushing the buffers in a larger run, we encourage larger writes at the kernel level and less interleaving of WAL flushes and data file writes. The effect is mainly noticeable with multiple parallel COPY FROMs. In this case, client backends achieve higher write throughput and end up spending less time waiting on acquiring the lock to flush WAL. Larger flush operations also mean less time waiting for flush operations at the kernel level. The heuristic for eager eviction is to only flush buffers in the strategy ring which do not require a WAL flush. This patch also is a step toward AIO writes. Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Earlier version Reviewed-by: Kirill Reshke <reshkekirill@gmail.com> Discussion: https://postgr.es/m/2FA0BAC7-5413-4ABD-94CA-4398FE77750D%40gmail.com Discussion: https://postgr.es/m/flat/CAAKRu_Yjn4mvN9NBxtmsCQSGwup45CoA4e05nhR7ADP-v0WCig%40mail.gmail.com

Implement write combining for users of the bulkwrite buffer access strategy (e.g. COPY FROM). When the buffer access strategy needs to clean a buffer for reuse, it already opportunistically flushes some other buffers. Now, combine any contiguous blocks from the same relation into larger writes and issue them with smgrwritev(). The performance benefit for COPY FROM is mostly noticeable for multiple concurrent COPY FROMs because a single COPY FROM is either CPU bound or bound by WAL writes. The infrastructure for flushing larger batches of IOs will be reused by checkpointer and other processes doing writes of dirty data. XXX: Because this sets in-place checksums for batches, it is not committable until additional infrastructure goes in place. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/flat/CAAKRu_bcWRvRwZUop_d9vzF9nHAiT%2B-uPzkJ%3DS3ShZ1GqeAYOw%40mail.gmail.com

In normal operation, XLogNeedsFlush() returns true if the flush ptr has not been advanced past the provided LSN. During normal recovery on a standby (not crash recovery), it return true if the minimum recovery point hasn't been advanced past the provided LSN. However, during an end-of-recovery checkpoint, the checkpointer flushes WAL, so XLogNeedsFlush() should compare the provided location with the flush pointer. Correct the logic in XLogNeedsFlush() to compare the LSN to the flush pointer when WAL inserts are allowed and the minimum recovery point otherwise. This is not an active bug because no current users of XLogNeedsFlush() temporarily allowed WAL inserts during recovery. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Jeff Davis <pgsql@j-davis.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/flat/CAAKRu_a1vZRZRWO3_jv_X13RYoqLRVipGO0237g5PKzPa2YX6g%40mail.gmail.com Discussion: https://postgr.es/m/flat/CAAKRu_bcWRvRwZUop_d9vzF9nHAiT%2B-uPzkJ%3DS3ShZ1GqeAYOw%40mail.gmail.com

This is useful for checkpointer write combining -- which will be added in a future commit. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/2FA0BAC7-5413-4ABD-94CA-4398FE77750D%40gmail.com

When the checkpointer writes out dirty buffers, writing multiple contiguous blocks as a single IO is a substantial performance improvement. The checkpointer is usually bottlenecked on IO, so issuing larger IOs leads to increased write throughput and faster checkpoints. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/2FA0BAC7-5413-4ABD-94CA-4398FE77750D%40gmail.com

This branch was automatically generated by a robot using patches from an email thread registered at: https://commitfest.postgresql.org/patch/6043 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/CAAKRu_atZuU3gYY6hVVuvqDW+mfXM+fCWCyYODbZPesxyr=y6g@mail.gmail.com Author(s): Melanie Plageman

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Commits on Sep 13, 2025

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