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https://issues.apache.org/jira/browse/HBASE-5347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13209020#comment-13209020
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Phabricator commented on HBASE-5347:
------------------------------------
khemani has commented on the revision "[HBASE-5347] [jira] GC free memory
management in Level-1 Block Cache".
INLINE COMMENTS
src/main/java/org/apache/hadoop/hbase/KeyValue.java:2099 Stack, there is a
lot of cleanup needed. I will get back to your feedback soon.
Regarding the ReferenceQueue mechanism and the fact that it gets cleaned up
at best at GC speeds ... yes you are right that if all dead KVs ended up on
this reference-queue then this approach won't be any better. But if a
kv.deref() is called explicitly before the kv is put up for garbage collection
then that kv will not land on this reference-queue.
The reference-queue is only there to catch those instances where we might
have forgotten to do an explicit kv.deref(). Hopefully there won't be too many
such cases.
REVISION DETAIL
https://reviews.facebook.net/D1635
> 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
>
> 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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