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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15453) [Performance] Considering reverting HBASE-10015 - reinstate synchronized in StoreScanner
Date Mon, 21 Mar 2016 21:39:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15205211#comment-15205211
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Andrew Purtell commented on HBASE-15453:
----------------------------------------

The patch hurts a little on 7u and helps a little bit more on 8u on my open source laptop.
Magnitude of difference will vary by CPU generation too I'm sure.

On Intel Core i5 CPU M 520  @ 2.40GHz (cpufreq governor userspace freq 2.40GHz)

java version "1.7.0_79"
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

Without: 10 runs  mean:2077.1 sigma:91.84601243385582
With: 10 runs  mean:2782.6 sigma:116.52313075093717

---

java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

Without: 10 runs  mean:2129.6 sigma:75.55289537800653
With: 10 runs  mean:1805.7 sigma:30.870860046328477


> [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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