[jira] [Commented] (HBASE-21921) Notify users if the ByteBufAllocator is always allocating ByteBuffers from heap which means the increacing GC pressure

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

    [ https://issues.apache.org/jira/browse/HBASE-21921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16831498#comment-16831498 ] 

Anoop Sam John commented on HBASE-21921:
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U will provide the parts of UI and/or JMX also as part of this jira?  Ya we would need to expose the max BB count and cur free count.. How many times the on heap alloc happens.   Rate of on heap alloc also? (on heap alloc/total alloc reqs)?

> Notify users if the ByteBufAllocator is always allocating ByteBuffers from heap which means the increacing GC pressure
> ----------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-21921
>                 URL: https://issues.apache.org/jira/browse/HBASE-21921
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Zheng Hu
>            Assignee: Zheng Hu
>            Priority: Minor
>         Attachments: HBASE-21921.HBASE-21879.v01.patch
>
>
> As the javadoc of ByteBuffAllocator says: 
> {code}
> There's possible that the desired memory size is large than ByteBufferPool has, we'll downgrade to allocate ByteBuffers from heap which meaning the GC pressure may increase again. Of course, an better way is increasing the ByteBufferPool size if we detected this case. 
> {code}
> So I think we need some messages to remind the user that an larger ByteBufferPool size may be better if the allocator allocate ByteBuffer from heap frequently. 



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