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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15453) Considering reverting HBASE-10015 - reinstance synchronized in StoreScanner
Date Mon, 14 Mar 2016 04:24:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15192726#comment-15192726
] 

Lars Hofhansl commented on HBASE-15453:
---------------------------------------

Work machine (OpenJDK Runtime Environment (IcedTea 2.6.4) (7u95-2.6.4))
Intrinsic:
10 runs  mean:1749.9 sigma:25.76606295109907
10 runs  mean:1782.8 sigma:54.50100916496868

Explicit:
10 runs  mean:1487.6 sigma:117.99169462296913
10 runs  mean:1479.6 sigma:41.01511916354749

So on JDK7 the explicit locks are (still inexplicably) faster.


> Considering reverting HBASE-10015 - reinstance synchronized in StoreScanner
> ---------------------------------------------------------------------------
>
>                 Key: HBASE-15453
>                 URL: https://issues.apache.org/jira/browse/HBASE-15453
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         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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