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From "Hiroshi Ikeda (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15716) HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read
Date Tue, 05 Jul 2016 01:33:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15361878#comment-15361878
] 

Hiroshi Ikeda commented on HBASE-15716:
---------------------------------------

I found there is some changes on the master around this (HBASE-15948). Using a blocking queue
doesn't make sense. Moreover, unlike HADOOP-9956, calling the method {{add}} just crash the
server if any. Also I don't understand why HBASE-15948 intentionally changes the code and
leaks sockets which are failed to initialize. Introducing another thread (Timer) make the
situation chaotic, and I give up.

> 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.implementation.using.ScannerReadPoints.branch-1.patch, 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, HBASE-15716.branch-1.001.patch, HBASE-15716.branch-1.002.patch,
HBASE-15716.branch-1.003.patch, HBASE-15716.branch-1.004.patch, HBASE-15716.branch-1.005.patch,
ScannerReadPoints.java, ScannerReadPoints.v2.java, 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, Screen Shot 2016-06-30 at 9.52.52 PM.png, Screen Shot 2016-06-30 at 9.54.08
PM.png, TestScannerReadPoints.java, before_after.png, current-branch-1.vs.NoSynchronization.vs.Patch.png,
hits.png, remove.locks.patch, 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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