Anoop Sam John commented on HBASE-16401:

I am checking this more and raising sub tasks for issues..  Related to evicted 
block count which is used for the tune decision there is some issue
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
Will raise a sub task to fix this issue.

> Enable HeapMemoryManager by default in 2.0
> ------------------------------------------
>                 Key: HBASE-16401
>                 URL: https://issues.apache.org/jira/browse/HBASE-16401
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: stack
>            Priority: Critical
>             Fix For: 2.0.0
> Back in HBASE-5349, on the end of the issue, we talked about enabling 
> HeapMemoryManager by default. Lets do it for 2.0 with some conservative 
> boundaries. Do it now so we have some experience running it before release.

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