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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15716) HRegion#RegionScannerImpl scannerReadPoints synchronization constrains random read
Date Tue, 14 Jun 2016 18:04:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15330047#comment-15330047
] 

stack commented on HBASE-15716:
-------------------------------

One note is that there is also registration of Store Scanners with the changed readers observers
which is another 'hump' like the one reported here that is not as onerous to cross but now
shows up after I clear out our blocking executor queues. That needs to be addressed too.

Again to say that after hacking out this region scanner lock AND the Store registration of
a listener, I get about a 10% boost on random read workloadc which could be more if we weren't
bottlnecked on returning the result.

> 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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