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From "Yu Sun (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16300) LruBlockCache.CACHE_FIXED_OVERHEAD should calculate LruBlockCache size correctly
Date Fri, 29 Jul 2016 01:47:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15398566#comment-15398566
] 

Yu Sun commented on HBASE-16300:
--------------------------------

this small bug likely imported by {{HBASE-14793}}, in which add a new long field {{private
final long maxBlockSize;}} to LruBlockCache, but when update:
{code}
   public final static long CACHE_FIXED_OVERHEAD = ClassSize.align(
-      (3 * Bytes.SIZEOF_LONG) + (9 * ClassSize.REFERENCE) +
-      (5 * Bytes.SIZEOF_FLOAT) + Bytes.SIZEOF_BOOLEAN
+      (3 * Bytes.SIZEOF_LONG) + (10 * ClassSize.REFERENCE) +
+      (5 * Bytes.SIZEOF_FLOAT) + (2 * Bytes.SIZEOF_BOOLEAN)
       + ClassSize.OBJECT);
{code}

the long field are taken as a reference.

> LruBlockCache.CACHE_FIXED_OVERHEAD should calculate LruBlockCache size correctly
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-16300
>                 URL: https://issues.apache.org/jira/browse/HBASE-16300
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Yu Sun
>            Assignee: Yu Sun
>         Attachments: HBASE-16300-v1.patch
>
>
> in current master {{LruBlockCache}},  CACHE_FIXED_OVERHEAD is calculated as this:
> {code}
>   public final static long CACHE_FIXED_OVERHEAD = ClassSize.align(
>       (3 * Bytes.SIZEOF_LONG) + (10 * ClassSize.REFERENCE) +
>       (5 * Bytes.SIZEOF_FLOAT) + (2 * Bytes.SIZEOF_BOOLEAN)
>       + ClassSize.OBJECT);
> {code}
> after some investigation. I think there are some wrong here, {{class LruBlockCache}},
except static varible(which is belongs to class), there are 4 long varibles(maxBlockSize,maxSize,blockSize
and overhead), 9 reference varibles and 2 boolean varibles, so the above code will not calculate
LruBlockCache instance size correctly.
> current related ut not failed mostly due to the result is 8 bytes aligned.



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