[jira] [Updated] (HBASE-28256) Enhance ByteBufferUtils.readVLong to read more bytes at a time

["Bryan Beaudreault (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-28256?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bryan Beaudreault updated HBASE-28256:
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    Summary: Enhance ByteBufferUtils.readVLong to read more bytes at a time  (was: Enhance ByteBufferUtils.readVLong to read 8 bytes at a time)

> Enhance ByteBufferUtils.readVLong to read more 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
>            Priority: Major
>         Attachments: ReadVLongBenchmark.zip, 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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