[jira] [Updated] (HBASE-6603) RegionMetricsStorage.incrNumericMetric is called too often

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

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

Lars Hofhansl updated HBASE-6603:
---------------------------------

    Attachment: 6503-0.96.txt

Here's a version of the HBASE-6217 patch for trunk.

In an extreme test with Gets of 60.000 columns the time went from about 164ms/iteration to 124ms.

                
> 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: Lars Hofhansl
>             Fix For: 0.96.0, 0.94.2
>
>         Attachments: 6503-0.96.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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