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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 22:07:57 GMT

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

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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