[jira] [Commented] (HBASE-15716) HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15262473#comment-15262473 ] 

Hadoop QA commented on HBASE-15716:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | {color:red} patch {color} | {color:red} 0m 3s {color} | {color:red} HBASE-15716 does not apply to master. Rebase required? Wrong Branch? See https://yetus.apache.org/documentation/0.2.1/precommit-patchnames for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12801270/15716.wip.more_to_be_done.patch |
| JIRA Issue | HBASE-15716 |
| Console output | https://builds.apache.org/job/PreCommit-HBASE-Build/1656/console |
| Powered by | Apache Yetus 0.2.1   http://yetus.apache.org |


This message was automatically generated.



> HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-15716
>                 URL: https://issues.apache.org/jira/browse/HBASE-15716
>             Project: HBase
>          Issue Type: Bug
>          Components: Performance
>            Reporter: stack
>            Assignee: stack
>         Attachments: 15716.prune.synchronizations.patch, 15716.prune.synchronizations.v3.patch, 15716.prune.synchronizations.v4.patch, 15716.prune.synchronizations.v4.patch, 15716.wip.more_to_be_done.patch, Screen Shot 2016-04-26 at 2.05.45 PM.png, Screen Shot 2016-04-26 at 2.06.14 PM.png, Screen Shot 2016-04-26 at 2.07.06 PM.png, Screen Shot 2016-04-26 at 2.25.26 PM.png, Screen Shot 2016-04-26 at 6.02.29 PM.png, Screen Shot 2016-04-27 at 9.49.35 AM.png, current-branch-1.vs.NoSynchronization.vs.Patch.png, hits.png, remove_cslm.patch
>
>
> Here is a [~lhofhansl] special.
> When we construct the region scanner, we get our read point and then store it with the scanner instance in a Region scoped CSLM. This is done under a synchronize on the CSLM.
> This synchronize on a region-scoped Map creating region scanners is the outstanding point of lock contention according to flight recorder (My work load is workload c, random reads).



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