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https://issues.apache.org/jira/browse/HBASE-28025?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17755667#comment-17755667
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Becker Ewing commented on HBASE-28025:
--------------------------------------
Thank you for the review [~zhangduo]!
*Benchmarking Methodology*
I've done some benchmarking of the normal java implementation vs. the optimized
unsafe implementation across various buffer/array types and key sizes. The test
methodology was for each key size (2, 36, 135) generate buffers & arrays with
identical contents that differ only in the last byte. Call findCommonPrefix for
every possible buffer/array combination on both the pure java implementation
and the unsafe implementation. My environment is: JMH 1.37, JVM: JDK 11.0.12,
OpenJDK 64-Bit Server VM, 11.0.12+7, CPU: Apple M1 Max. Benchmarks were run by
compiling the attached source and running it.
*Raw Data*
||Benchmark Name||Key Size||Pure Java Implementation Average Time
(ns/op)||Unsafe Implementation Average Time (ns/op)||
|findCommonPrefix_Array_Array|2|4.170 ± 0.122|4.698 ± 0.104|
| |36|14.971 ± 0.631|8.702 ± 0.167|
| |135|39.706 ± 3.025|14.968 ± 0.316|
|findCommonPrefix_OffHeapBB_Array|2|4.378 ± 0.173|4.198 ± 0.285|
| |36|19.554 ± 0.312|7.563 ± 0.053|
| |135|60.766 ± 5.392|13.639 ± 0.189|
|findCommonPrefix_OffHeapBB_OffHeapBB|2|4.499 ± 0.401|4.882 ± 0.137|
| |36|22.649 ± 0.574|7.947 ± 0.183|
| |135|72.753 ± 2.831|12.699 ± 0.121|
|findCommonPrefix_OnHeapBB_OnHeapBB|2|7.626 ± 0.128|7.642 ± 0.333|
| |36|26.966 ± 0.201|12.177 ± 0.632|
| |135|114.375 ± 8.032|18.104 ± 0.629|
*Summary*
The new implementation is seems to be about equal or slightly slower when using
a keySize of 2. As key size increases (particularly gets larger than 8),
performance rapidly increases for the newer Unsafe variant of the code. It's
about ~70% faster at a keySize of 36 and ~260% faster at a keySize of 135.
> Enhance ByteBufferUtils.findCommonPrefix to compare 8 bytes each time
> ---------------------------------------------------------------------
>
> Key: HBASE-28025
> URL: https://issues.apache.org/jira/browse/HBASE-28025
> Project: HBase
> Issue Type: Improvement
> Components: Performance
> Affects Versions: 2.5.4
> Reporter: Becker Ewing
> Assignee: Becker Ewing
> Priority: Major
> Attachments: HBASE-28025_jmh_benchmarks_src.zip, benchmark_results.txt
>
>
> Currently, the `ByteBufferUtils.findCommonPrefix family of methods compare
> two buffers a single byte at a time. In reviewing the patch for HBASE-28012,
> [~zhangduo] suggested that the ByteBufferUtils.findCommonPrefix methods could
> be enhanced to compare 8 bytes at a time like the
> ByteBufferUtils.compareToUnsafe family of methods already does (which was
> added in HBASE-12345)
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