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Date: Wed, 16 Oct 2013 23:09:42 +0000 (UTC)
From: "Himanshu Vashishtha (JIRA)" <jira@apache.org>
To: dev@hbase.apache.org
Message-ID: <JIRA.12674216.1381964917232.76910.1381964982078@arcas>
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Subject: [jira] [Created] (HBASE-9785) Fix heap size reporting in HRegion
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Himanshu Vashishtha created HBASE-9785:
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             Summary: Fix heap size reporting in HRegion
                 Key: HBASE-9785
                 URL: https://issues.apache.org/jira/browse/HBASE-9785
             Project: HBase
          Issue Type: Bug
    Affects Versions: 0.96.0
            Reporter: Himanshu Vashishtha
             Fix For: 0.98.0, 0.96.1


The size reported by Fixed_Overhead variable in HRegion misses out on a boolean variable. TestHeapSize doesn't report it because of the alignment we do to make it multiple of 8. 

The equation for HRegion heap usage from Fixed_Overhead is: 
Fixed_Overhead = align(100 + 42*ref + 1 arr) = align(284) = 288 on a 32 bit vm
(On a 32 bit vm, 1 ref = 4bytes, 1 arr = 16 bytes)

The equation formed using reflection (in Classsize) is:
Expected_Overehead = align(101 + 42*ref + 1arr) = align(285) = 288.
So, the testHeapSize doesn't fail currently.

But if I add a reference (did in last patch in 8741), it starts failing because, now the equations are:
Fixed_Overhead = align(100 + 43*ref + 1 arr) = align(288) = 288
Expected_Overhead = align(101 + 43*ref + 1 arr) = align(289) = 296.


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