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https://issues.apache.org/jira/browse/SPARK-26337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16717665#comment-16717665
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ASF GitHub Bot commented on SPARK-26337:
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kiszk commented on issue #23284: [SPARK-26337][SQL][TEST] Add benchmark for
LongToUnsafeRowMap
URL: https://github.com/apache/spark/pull/23284#issuecomment-446299651
To be honest, I cannot understand why the original performance degradation
occurred.
I think that read/write of `long` value does not require any sychronization
or memory barrier without declaring `volatile`.
At this [PR](https://github.com/apache/spark/pull/23204/files),
`numKeyLookups` and `numProbes` are non-volatile long variables. I confirmed it
by decompling a class file. However, I have no time to disassemble the
generated code today and tomorrow.
[Here](https://stackoverflow.com/questions/25173208/value-integrity-guarantee-for-concurrent-long-writes-in-64-bit-openjdk-7-8)
is an article that addresses the similar topic regarding `static long`.
cc @rednaxelafx
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> Add benchmark for LongToUnsafeRowMap
> ------------------------------------
>
> Key: SPARK-26337
> URL: https://issues.apache.org/jira/browse/SPARK-26337
> Project: Spark
> Issue Type: Test
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Liang-Chi Hsieh
> Priority: Major
>
> Regarding the performance issue of SPARK-26155, I think it is better to add a
> benchmark for LongToUnsafeRowMap which is the root cause of performance
> regression. It can be easier to show performance difference between different
> metric implementation in LongToUnsafeRowMap.
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