[jira] [Created] (CASSANDRA-21677) Pool Native Zstd Contexts in Plain ZstdCompressor

["Yifan Cai (Jira)" <ji...@apache.org>]

Yifan Cai created CASSANDRA-21677:
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             Summary: Pool Native Zstd Contexts in Plain ZstdCompressor
                 Key: CASSANDRA-21677
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-21677
             Project: Apache Cassandra
          Issue Type: Improvement
          Components: Feature/Compression
            Reporter: Yifan Cai


ZstdCompressorBase.compress()/uncompress() call Zstd's static one-shot helpers (Zstd.compress, Zstd.decompress, Zstd.decompressByteArray), each of which allocates a native ZSTD_CCtx/ZSTD_DCtx and frees it before returning, once per chunk. 

According to CASSANDRA-21672, profiling of the dictionary-compression path found roughly 6.5% of node CPU in ZSTD_createCCtx alone at small chunk sizes, and the same per-chunk allocation cost applies to plain, non-dictionary Zstd compression, which is unaffected by that work. ZstdCompressor should pool a reusable ZstdCompressCtx/ZstdDecompressCtx per compressor instance, instead of allocating and freeing a native context on every chunk.

That said, the plain ZstdCompressor is likely less impacted by the per chunk allocation, as it typically requires larger chunk size to achieve a good compression ratio. The effect of per chunk allocation is more significant for small chunks such as 4KiB.



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