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https://issues.apache.org/jira/browse/HBASE-6603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13437636#comment-13437636
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Lars Hofhansl commented on HBASE-6603:
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Sure. Just make a 0.94/0.96 patch there. Patch there looks good to me. (copykv
is gone now, though).
> 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
>
>
> 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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