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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4027) Enable direct byte buffers LruBlockCache
Date Fri, 24 Jun 2011 19:29:47 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13054639#comment-13054639
] 

Jonathan Gray commented on HBASE-4027:
--------------------------------------

In the new HFile v2 over in HBASE-3857 the block cache interface changes from ByteBuffer to
HeapSize.  So you can now put anything you want into the cache that implements HeapSize (there
is a new HFileBlock that is used in HFile v2).

One big question is whether you're going to make copies out of the direct byte buffers on
each read of that block, or if you're going to change KeyValue to use the ByteBuffer interface
(or some other) instead of the byte[] directly.  With a DBB you can't get access to an underlying
byte[].

> Enable direct byte buffers LruBlockCache
> ----------------------------------------
>
>                 Key: HBASE-4027
>                 URL: https://issues.apache.org/jira/browse/HBASE-4027
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Jason Rutherglen
>            Priority: Minor
>
> Java offers the creation of direct byte buffers which are allocated outside of the heap.
> They need to be manually free'd, which can be accomplished using an documented {{clean}}
method.
> The feature will be optional.  After implementing, we can benchmark for differences in
speed and garbage collection observances.

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