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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10015) Replace intrinsic locking with explicit locks in StoreScanner
Date Wed, 27 Nov 2013 07:59:36 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13833557#comment-13833557
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Hudson commented on HBASE-10015:
--------------------------------

FAILURE: Integrated in HBase-0.94 #1212 (See [https://builds.apache.org/job/HBase-0.94/1212/])
HBASE-10015 Replace intrinsic locking with explicit locks in StoreScanner (larsh: rev 1545840)
* /hbase/branches/0.94/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java


> Replace intrinsic locking with explicit locks in StoreScanner
> -------------------------------------------------------------
>
>                 Key: HBASE-10015
>                 URL: https://issues.apache.org/jira/browse/HBASE-10015
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>              Labels: performance
>             Fix For: 0.98.0, 0.96.1, 0.94.15
>
>         Attachments: 10015-0.94-lock.txt, 10015-0.94-new-sample.txt, 10015-0.94-v2.txt,
10015-0.94-v3.txt, 10015-0.94-v4.txt, 10015-0.94-withtest.txt, 10015-0.94.txt, 10015-trunk-lock.txt,
10015-trunk-v2.txt, 10015-trunk-v3.txt, 10015-trunk-v4.txt, 10015-trunk-v4.txt, 10015-trunk-v4.txt,
10015-trunk.txt, TestLoad.java
>
>
> Did some more profiling (this time with a sampling profiler) and StoreScanner.peek()
showed up a lot in the samples. At first that was surprising, but peek is synchronized, so
it seems a lot of the sync'ing cost is eaten there.
> It seems the only reason we have to synchronize all these methods is because a concurrent
flush or compaction can change the scanner stack, other than that only a single thread should
access a StoreScanner at any given time.
> So replaced updateReaders() with some code that just indicates to the scanner that the
readers should be updated and then make it the using thread's responsibility to do the work.
> The perf improvement from this is staggering. I am seeing somewhere around 3x scan performance
improvement across all scenarios.
> Now, the hard part is to reason about whether this is 100% correct. I ran TestAtomicOperation
and TestAcidGuarantees a few times in a loop, all still pass.
> Will attach a sample patch.



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