[jira] [Created] (HBASE-17819) Reduce the heap overhead for BucketCache

["Anoop Sam John (JIRA)" <ji...@apache.org>]

Anoop Sam John created HBASE-17819:
--------------------------------------

             Summary: Reduce the heap overhead for BucketCache
                 Key: HBASE-17819
                 URL: https://issues.apache.org/jira/browse/HBASE-17819
             Project: HBase
          Issue Type: Sub-task
            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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