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https://issues.apache.org/jira/browse/HBASE-10015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13833035#comment-13833035
 ] 

Hadoop QA commented on HBASE-10015:
-----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12615867/10015-trunk-lock.txt
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include 
any new or modified tests.
                        Please justify why no new tests are needed for this 
patch.
                        Also please list what manual steps were performed to 
verify this patch.

    {color:green}+1 hadoop1.0{color}.  The patch compiles against the hadoop 
1.0 profile.

    {color:green}+1 hadoop2.0{color}.  The patch compiles against the hadoop 
2.0 profile.

    {color:red}-1 javadoc{color}.  The javadoc tool appears to have generated 1 
warning messages.

    {color:red}-1 javac{color}.  The applied patch generated 4 javac compiler 
warnings (more than the trunk's current 0 warnings).

    {color:red}-1 findbugs{color}.  The patch appears to introduce 1 new 
Findbugs (version 1.3.9) warnings.

    {color:red}-1 release audit{color}.  The applied patch generated 1 release 
audit warnings (more than the trunk's current 0 warnings).

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines 
longer than 100

    {color:red}-1 site{color}.  The patch appears to cause mvn site goal to 
fail.

    {color:green}+1 core tests{color}.  The patch passed unit tests in .

Test results: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//testReport/
Release audit warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/patchReleaseAuditProblems.txt
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-prefix-tree.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-client.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-protocol.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop1-compat.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-examples.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-thrift.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Console output: 
https://builds.apache.org/job/PreCommit-HBASE-Build/8000//console

This message is automatically generated.

> 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
>         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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