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https://issues.apache.org/jira/browse/HBASE-5347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13211598#comment-13211598
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Prakash Khemani commented on HBASE-5347:
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Thanks for the reviews. I will make another pass pretty soon.
Todd, What you have suggested will not help when a piece of code wants to
bump up the reference count because it is keeping the reference to the
object in some state variable. (for example the store scanner does it
after a flush). But your suggestion will work in those cases where a piece
of code forgets to decrement the reference count. The current patch also
has similar characteristics. It cannot automatically bump up the reference
count. But if it forgets to do dereference and decrement the ref count
then it relies on WeakReferences and garbage collection to do the same.
On 2/19/12 12:56 AM, "Zhihong Yu (Commented) (JIRA)" <[email protected]>
> GC free memory management in Level-1 Block Cache
> ------------------------------------------------
>
> Key: HBASE-5347
> URL: https://issues.apache.org/jira/browse/HBASE-5347
> Project: HBase
> Issue Type: Improvement
> Reporter: Prakash Khemani
> Assignee: Prakash Khemani
> Attachments: D1635.5.patch
>
>
> On eviction of a block from the block-cache, instead of waiting for the
> garbage collecter to reuse its memory, reuse the block right away.
> This will require us to keep reference counts on the HFile blocks. Once we
> have the reference counts in place we can do our own simple
> blocks-out-of-slab allocation for the block-cache.
> This will help us with
> * reducing gc pressure, especially in the old generation
> * making it possible to have non-java-heap memory backing the HFile blocks
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