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https://issues.apache.org/jira/browse/HBASE-17819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16088839#comment-16088839
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Anoop Sam John commented on HBASE-17819:
----------------------------------------

We have a config to say whether blocks belonging to an HFile to be evicted when 
the file is closed. 
key : 'hbase.rs.evictblocksonclose'
This defaults to false only.
Means the blocks wont be forcefully evicted when a file is closed but 
eventually the LRU nature will remove these blocks.
This is what was happening before we had CompactedHFilesDischarger? 
[~ram_krish]?
Now CompactedHFilesDischarger seems not considering this config!

> Reduce the heap overhead for BucketCache
> ----------------------------------------
>
>                 Key: HBASE-17819
>                 URL: https://issues.apache.org/jira/browse/HBASE-17819
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0
>
>
> We keep Bucket entry map in BucketCache.  Below is the math for heapSize for 
> the key , value into this map.
> BlockCacheKey
> ---------------
> String hfileName  -  Ref  - 4
> long offset  - 8
> BlockType blockType  - Ref  - 4
> boolean isPrimaryReplicaBlock  - 1
> Total  =  12 (Object) + 17 = 29
> BucketEntry
> ------------
> int offsetBase  -  4
> int length  - 4
> byte offset1  -  1
> byte deserialiserIndex  -  1
> long accessCounter  -  8
> BlockPriority priority  - Ref  - 4
> volatile boolean markedForEvict  -  1
> AtomicInteger refCount  -  16 + 4
> long cachedTime  -  8
> Total = 12 (Object) + 51 = 63
> ConcurrentHashMap Map.Entry  -  40
> blocksByHFile ConcurrentSkipListSet Entry  -  40
> Total = 29 + 63 + 80 = 172
> For 10 million blocks we will end up having 1.6GB of heap size.  
> This jira aims to reduce this as much as possible



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