Anoop Sam John updated HBASE-16650:
      Resolution: Fixed
    Hadoop Flags: Incompatible change,Reviewed
    Release Note: Changed tracking of evictedBlocks count NOT to include 
evictions of blocks for a removed HFile. HFiles gets removed after compaction
          Status: Resolved  (was: Patch Available)

Pushed to master. Thanks for the review Stack.
Though it is applicable in 1.x branches also, not committing.  HeapMemory 
tuning is default ON there.  This is part of making it ready for turning ON by 

> Wrong usage of BlockCache eviction stat for heap memory tuning
> --------------------------------------------------------------
>                 Key: HBASE-16650
>                 URL: https://issues.apache.org/jira/browse/HBASE-16650
>             Project: HBase
>          Issue Type: Sub-task
>    Affects Versions: 1.0.0
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0, 1.4.0
>         Attachments: HBASE-16650.patch, HBASE-16650_V2.patch, 
> HBASE-16650_V3.patch, HBASE-16650_V4.patch, HBASE-16650_V5.patch
> 1. We use the stat evictedBlocksCount - A block can get evicted because of 
> eviction thread due to lack of space or because of removal of an HFile itself 
> (After a compaction). We should not consider the latter in the tune decision 
> at all. These are actually invalidation of blocks. Should the stat counter 
> itself not use this count of evicted blocks? I think yes. This will give 
> wrong message to users that there are lot of real eviction happening.
> 2. In case L1+ L2 combined block cache, what we use is the sum of evictions 
> from both. But we will be tuning L1 size alone. Eviction count from L2 should 
> not affect the tuning of L1

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