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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-15716) HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read
Date Mon, 27 Jun 2016 15:30:52 GMT

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

stack updated HBASE-15716:
--------------------------
    Attachment: remove.locks.patch

Patch w/ alternate implementation for registering region scanners (for consideration -- two
volatile reads in place of synchronization blocks...) and that removes unnecessary locks.
Changes nature of the thread dumps so we are now just blocking reading and writing on channels
(for most part -- some work to be done still). Doesn't get us much... maybe 5-10% on throughput.
Let me see...

> 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.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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