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Patrick Steinhardt 5473aca376 reftable/merged: really reuse buffers to compute record keys
In 829231dc20 (reftable/merged: reuse buffer to compute record keys,
2023-12-11), we have refactored the merged iterator to reuse a pair of
long-living strbufs by relying on the fact that `reftable_record_key()`
tries to reuse already allocated strbufs by calling `strbuf_reset()`,
which should give us significantly fewer reallocations compared to the
old code that used on-stack strbufs that are allocated for each and
every iteration. Unfortunately, we called `strbuf_release()` on these
long-living strbufs that we meant to reuse on each iteration, defeating
the optimization.

Fix this performance issue by not releasing those buffers on iteration
anymore, where we instead rely on `merged_iter_close()` to release the
buffers for us.

Using `git show-ref --quiet` in a repository with ~350k refs this leads
to a significant drop in allocations. Before:

    HEAP SUMMARY:
        in use at exit: 21,163 bytes in 193 blocks
      total heap usage: 1,410,148 allocs, 1,409,955 frees, 61,976,068 bytes allocated

After:

    HEAP SUMMARY:
        in use at exit: 21,163 bytes in 193 blocks
      total heap usage: 708,058 allocs, 707,865 frees, 36,783,255 bytes allocated

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-03 09:54:21 -08:00
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reftable reftable/merged: really reuse buffers to compute record keys 2024-01-03 09:54:21 -08:00
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COPYING
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GIT-VERSION-GEN Start the 2.44 cycle 2023-12-09 16:37:51 -08:00
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git.c
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INSTALL Merge branch 'js/update-urls-in-doc-and-comment' 2023-12-18 14:10:12 -08:00
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Makefile Merge branch 'js/update-urls-in-doc-and-comment' 2023-12-18 14:10:12 -08:00
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merge-ll.c
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pager.c
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parallel-checkout.c
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parse-options-cb.c
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README.md
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remote-curl.c
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repository.c
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serve.c
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shared.mak
shell.c
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unix-socket.c
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unpack-trees.c
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url.c
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usage.c
userdiff.c
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varint.c
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version.c
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worktree.c
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xdiff-interface.h

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