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https://issues.apache.org/jira/browse/HBASE-17819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16405769#comment-16405769
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Anoop Sam John commented on HBASE-17819:
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It is now 1.64 GB. This patch as such reduces only 16 bytes per entry. So
not so much of difference. May be like 0.15 GB only.. The other item is the
skipList in BC which eats 40 bytes per entry. If that is also done, total can
be reduced to 1.1 GB. But that needs some more discussion.. I wanted the
simpler change to go in first. I had measured the object sizes using
java.lang.instrument.Instrumentation way also and the theory looks correct as
per that.
> 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
> Priority: Critical
> Fix For: 2.0.0
>
> Attachments: HBASE-17819_V1.patch, HBASE-17819_V2.patch,
> HBASE-17819_V3.patch, HBASE-17819_new_V1.patch, HBASE-17819_new_V1.patch
>
>
> 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 = align(12 (Object) + 17 )= 32
> 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 = align(12 (Object) + 51) = 64
> ConcurrentHashMap Map.Entry - 40
> blocksByHFile ConcurrentSkipListSet Entry - 40
> Total = 32 + 64 + 80 = 176
> 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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