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https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15261585#comment-15261585
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stack commented on HBASE-15716:
-------------------------------
Thank you the helpful review [~ikeda] Do you a fault other than below in this
approach?
bq. ...and then, the smallest readpoint goes back.
Can you say more please? I do not follow how it goes 'back' since we do
readPoint = currentReadPoint;
at the bottom of the loop.
Yes, the readpoint moves independently....
I like the way you think on scannerReadPoints having too much info... Yes, if
we miss the close, a reference to the Scanner will be held here. That is a good
point.
I like your idea too of the skipping out when IL is READ_UNCOMMITTED. Let me do
that.
Let me look at an implementation using your suggested types....
Thanks again for the review.
> HRegion#RegionScannerImpl scannerReadPoints synchronization costs
> -----------------------------------------------------------------
>
> 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,
> 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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