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https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack updated HBASE-15716:
--------------------------
Attachment: before_after.png
Test run showing 5-6% improvement.
All Readers are either reading (down in channel read) or else they are doing
Semaphore release to go the fastpath.
Handlers are doing channel writes (responses), putting the region scanner on
the Map of all outstanding Scanners (CHM -- the hash function in particular),
or they are trying to acquire Semaphore so can do the fastpath.
No locking other than down in the read/write (and Semaphores above).
Need to figure how to write replies faster.
> 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,
> HBASE-15716.branch-1.001.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, 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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