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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-6603) RegionMetricsStorage.incrNumericMetric is called too often
Date Fri, 17 Aug 2012 00:17:38 GMT
Lars Hofhansl created HBASE-6603:

             Summary: 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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