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