Jon Haddad created CASSANDRA-20428:
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Summary: Eliminate byte array allocation in ByteArrayAccessor.read
Key: CASSANDRA-20428
URL: https://issues.apache.org/jira/browse/CASSANDRA-20428
Project: Apache Cassandra
Issue Type: Improvement
Reporter: Jon Haddad
Attachments: allocation-reverse.html, image-2025-03-11-11-05-55-378.png
During compaction we allocate a new byte[] in ByteArrayAccessor.read. This is
one of the hottest paths in the codebase, hit during writes, compaction,
creating tables, and possibly others. In my performance tests using default
compaction settings of 64MB I see this responsible for 40% of allocations.
This is largely what drives GC pause frequency and duration. If we are able to
eliminate the O(N) allocations performed here, this might be one of the best
optimizations we could do for the number of things it touches.
Allocation profile attached.
!image-2025-03-11-11-05-55-378.png|width=514,height=269!
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