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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-15716) HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read
Date Fri, 01 Jul 2016 04:57:11 GMT

     [ https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

stack updated HBASE-15716:
--------------------------
    Attachment: Screen Shot 2016-06-30 at 9.54.08 PM.png
                Screen Shot 2016-06-30 at 9.52.52 PM.png

Before and after humps from a regionserver doing heavy workloadc (the trough is me doing the
JFR pull).

Also include picture of our JFR in JMC where it shows the thousands of contention points for
registration of region scanner as now gone.

Here are the lines from honest profiler flat view... before:

   62   (t 19.4,s  0.2) org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl::<init>

and after:

21   (t 18.9,s  0.8) org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl::<init>


> 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, ScannerReadPoints.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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