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https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266144#comment-15266144
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stack commented on HBASE-15716:
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[~ikeda We continue conservative here, w/o change. I like your suggestion that
we could change how we do scanner readpoint and that we might be able to skip
registering such a scanner in scannerReadPoints but need to do some more work
in here; until that is done, no change made.
> 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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