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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HBASE-6603) RegionMetricsStorage.incrNumericMetric is called too often
Date Mon, 20 Aug 2012 23:44:38 GMT

     [ https://issues.apache.org/jira/browse/HBASE-6603?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lars Hofhansl resolved HBASE-6603.
----------------------------------

       Resolution: Fixed
    Fix Version/s:     (was: 0.92.2)

Turns out that 0.92 does not collect this metric, so backport is not needed.
                
> RegionMetricsStorage.incrNumericMetric is called too often
> ----------------------------------------------------------
>
>                 Key: HBASE-6603
>                 URL: https://issues.apache.org/jira/browse/HBASE-6603
>             Project: HBase
>          Issue Type: Bug
>          Components: performance
>            Reporter: Lars Hofhansl
>            Assignee: M. Chen
>             Fix For: 0.96.0, 0.94.2
>
>         Attachments: 6503-0.96.txt, 6603-0.94.txt
>
>
> Running an HBase scan load through the profiler revealed that RegionMetricsStorage.incrNumericMetric
is called way too often.
> It turns out that we make this call for *each* KV in StoreScanner.next(...).
> Incrementing AtomicLong requires expensive memory barriers.
> The observation here is that StoreScanner.next(...) can maintain a simple 
> long in its internal loop and only update the metric upon exit. Thus the AtomicLong is
not updated nearly as often.
> That cuts about 10% runtime from scan only load (I'll quantify this better soon).

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