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https://issues.apache.org/jira/browse/HBASE-1127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12664343#action_12664343
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stack commented on HBASE-1127:
------------------------------

Been looking at this more.  I can watch the GC doing Full, Full, Full, but our 
executor thread checking SoftValueMap reference queues is not clearing 
anything.  Then we OOME.  I tried various things including a thread per 
instance of BlockFSInputStream just blocked on the reference queue waiting for 
the GC to add stuff.  Odd is that even in this case, we OOME though we get a 
bit further.  Changing the interval between when our executor thread runs from 
10 seconds to 1 second makes it so the executor now does clearing of reference 
queues but again its not enough.  We'll OOME at about same place as we do when 
we have a thread per BlockFSInputStream instance (A thread per instance won't 
fly so this is good)

I'm going to look at this a little more.  In times of high memory pressure, its 
as though the GC gives up adding items to reference queues which wouldn't seem 
to make sense.  Given that we're up against the RC, I am currently thinking 
that I'll revert to having blockcache on by default and instead let users 
choose it explicitly (with the checker running every second).  I'll leave it on 
in catalog tables so meta content has block cache on.



> OOME running randomRead PE
> --------------------------
>
>                 Key: HBASE-1127
>                 URL: https://issues.apache.org/jira/browse/HBASE-1127
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>            Priority: Blocker
>             Fix For: 0.19.0
>
>
> Blockcache is misbehaving on TRUNK.  Something is broke.  We OOME about 20% 
> into the randomRead test.  Looking at heap, its all soft references.  
> Instrumenting the referencequeue, we're never clearing full gc'ing.  
> Something is off.

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