| commit | ce1f213cc91cf545736048f28117fe1de89b8134 | [log] [tgz] |
|---|---|---|
| author | Patrick Steinhardt <ps@pks.im> | Mon Apr 08 14:17:04 2024 +0200 |
| committer | Junio C Hamano <gitster@pobox.com> | Mon Apr 15 10:36:09 2024 -0700 |
| tree | 3e8401f9a1682045caa99e8e94211da7f9716eab | |
| parent | 15a60b747e4f0e0d11353f8e89bc9ce7b36c5512 [diff] |
reftable/block: reuse `zstream` state on inflation
When calling `inflateInit()` and `inflate()`, the zlib library will
allocate several data structures for the underlying `zstream` to keep
track of various information. Thus, when inflating repeatedly, it is
possible to optimize memory allocation patterns by reusing the `zstream`
and then calling `inflateReset()` on it to prepare it for the next chunk
of data to inflate.
This is exactly what the reftable code is doing: when iterating through
reflogs we need to potentially inflate many log blocks, but we discard
the `zstream` every single time. Instead, as we reuse the `block_reader`
for each of the blocks anyway, we can initialize the `zstream` once and
then reuse it for subsequent inflations.
Refactor the code to do so, which leads to a significant reduction in
the number of allocations. The following measurements were done when
iterating through 1 million reflog entries. Before:
HEAP SUMMARY:
in use at exit: 13,473 bytes in 122 blocks
total heap usage: 23,028 allocs, 22,906 frees, 162,813,552 bytes allocated
After:
HEAP SUMMARY:
in use at exit: 13,473 bytes in 122 blocks
total heap usage: 302 allocs, 180 frees, 88,352 bytes allocated
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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