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https://issues.apache.org/jira/browse/HBASE-15453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15209184#comment-15209184
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stack commented on HBASE-15453:
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JDK7 is dead.
> [Performance] Considering reverting HBASE-10015 - reinstate synchronized in
> StoreScanner
> ----------------------------------------------------------------------------------------
>
> Key: HBASE-15453
> URL: https://issues.apache.org/jira/browse/HBASE-15453
> Project: HBase
> Issue Type: Improvement
> Components: Performance
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Critical
> Attachments: 15453-0.98.txt
>
>
> In HBASE-10015 back then I found that intrinsic locks (synchronized) in
> StoreScanner are slower that explicit locks.
> I was surprised by this. To make sure I added a simple perf test and many
> folks ran it on their machines. All found that explicit locks were faster.
> Now... I just ran that test again. On the latest JDK8 I find that now the
> intrinsic locks are significantly faster:
> (OpenJDK Runtime Environment (build 1.8.0_72-b15))
> Explicit locks:
> 10 runs mean:2223.6 sigma:72.29412147609237
> Intrinsic locks:
> 10 runs mean:1865.3 sigma:32.63755505548784
> I confirmed the same with timing some Phoenix scans. We can save a bunch of
> time by changing this back
> Arrghhh... So maybe it's time to revert this now...?
> (Note that in trunk due to [~ram_krish]'s work, we do not lock in
> StoreScanner anymore)
> I'll attach the perf test and a patch that changes lock to synchronized, if
> some folks could run this on 0.98, that'd be great.
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