compression: Allocate memory for LZ4_compressEnd #17156
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Before this change the code assumed that the destination temp. buffer always had enough free space for LZ4F_compressEnd operation. This change checks the free size before calling LZ4F_compressEnd and allocates a new buffer if necessary. Note that the free space required is computed using LZ4F_compressBound with a srcSize of 0. By looking at LZ4F_compressEnd it may appear that we can just check if 12 bytes are free in the destination buffer, whereas LZ4F_compressBound always assumes at least 65443 ie 65535 + block header size (4) + frame footer (4). However, lz4frame docstring for LZ4F_compressBound states that: "When srcSize==0, LZ4F_compressBound() provides an upper bound for LZ4F_flush() and LZ4F_compressEnd() instead." Similar directions are mentioned on LZ4 gh issues, so it is safer to be conservative and possibly allocate the extra bytes.
|
ducktape was retried in https://buildkite.com/redpanda/redpanda/builds/46350#018e50da-15de-45b8-8c76-6dc7f78fdfd3 |
nvartolomei
approved these changes
Mar 18, 2024
| output_sz - output_cursor < sz_for_compress_end) { | ||
| obuf.trim(output_cursor); | ||
| ret.append(std::move(obuf)); | ||
| obuf = ss::temporary_buffer<char>(sz_for_compress_end); |
|
/backport v23.3.x |
|
/backport v23.2.x |
This was referenced Mar 18, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Before this change the code assumed that the destination temp. buffer always had enough free space for
LZ4F_compressEndoperation. This change checks the free size before callingLZ4F_compressEndand allocates a new buffer if necessary.Note that the free space required is computed using
LZ4F_compressBoundwith asrcSizeof 0. By looking atLZ4F_compressEndcode, it may seem as if we can just check if 12 bytes are free in the destination buffer, whereasLZ4F_compressBoundalways assumes at least 65443 ie 65535 + block header size (4) + frame footer (4) possibly resulting in much larger allocation.However, lz4frame docstring for
LZ4F_compressBoundstates that:Additionally
LZ4F_compressEndmay also perform a flush which may need more than 12 bytes.Backports Required
Release Notes