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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6603) RegionMetricsStorage.incrNumericMetric is called too often
Date Fri, 17 Aug 2012 03:40:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13436538#comment-13436538
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Lars Hofhansl commented on HBASE-6603:
--------------------------------------

The patch in HBASE-6217 is similar to the change that I had made locally. (I did not add a
try/finally block, but instead updated the metric at the spots where the method returns. But
it's the same in principle)

Damn, and I was so proud of my profiling detective work. :)

So, should I close this as dup and mark HBASE-6217 against 0.94 and 0.96 also? Or leave HBASE-6217
against fb89 only and use this for the 0.94 and 0.96 patches?

                
> 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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