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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15453) [Performance] Considering reverting HBASE-10015 - reinstance synchronized in StoreScanner
Date Tue, 15 Mar 2016 03:51:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15194697#comment-15194697

Lars Hofhansl commented on HBASE-15453:

Note that HBASE-10015 in had many folks confirm the numbers. Explicit locks were better back
Also note that with JDK7 tested at work, Explicit locks were still better.
Only with JDK8 at home did I find that intrinsic locks (synchronized) was better.

It's not slam dunk, it depends on the JDK.

> [Performance] Considering reverting HBASE-10015 - reinstance 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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