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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6689) Partially Off Heap Memtables
Date Thu, 06 Mar 2014 22:45:51 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13923201#comment-13923201
] 

Benedict commented on CASSANDRA-6689:
-------------------------------------

The smallest direct byte buffer from Netty is on the order of 64-bytes minimum, whereas we
manage 24-bytes; plus for maintaining the allocation list we then need to have a separate
list, rather than chaining the allocations, so at least another 4-bytes overhead (more, but
in best case it tends to 4).

[https://github.com/netty/netty/blob/master/buffer/src/main/java/io/netty/buffer/AbstractByteBuf.java]
[https://github.com/netty/netty/blob/master/buffer/src/main/java/io/netty/buffer/UnpooledUnsafeDirectByteBuf.java]


> Partially Off Heap Memtables
> ----------------------------
>
>                 Key: CASSANDRA-6689
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6689
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>             Fix For: 2.1 beta2
>
>         Attachments: CASSANDRA-6689-small-changes.patch
>
>
> Move the contents of ByteBuffers off-heap for records written to a memtable.
> (See comments for details)



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