Becker Ewing created HBASE-28256:
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Summary: Enhance ByteBufferUtils.readVLong to read 8 bytes at a
time
Key: HBASE-28256
URL: https://issues.apache.org/jira/browse/HBASE-28256
Project: HBase
Issue Type: Improvement
Components: Performance
Reporter: Becker Ewing
Assignee: Becker Ewing
Attachments: async-prof-rs-cpu.html
Currently, ByteBufferUtils.readVLong is used to decode rows in all data block
encodings in order to read the memstoreTs field. For a data block encoding like
prefix, ByteBufferUtils.readVLong can surprisingly occupy over 50% of the CPU
time in BufferedEncodedSeeker.decodeNext (which can be quite a hot method in
seek operations).
Since memstoreTs will typically require at least 6 bytes to store, we could
look to vectorize the read path for readVLong to read 8 bytes at a time instead
of a single byte at a time (like in
https://issues.apache.org/jira/browse/HBASE-28025) in order to increase
performance.
Attached is a CPU flamegraph of a region server process which shows that we
spend a surprising amount of time in decoding rows from the DBE in
ByteBufferUtils.readVLong.
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