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From "Yang Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2252) arena allocation for memtables
Date Thu, 25 Aug 2011 18:44:37 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13091209#comment-13091209
] 

Yang Yang commented on CASSANDRA-2252:
--------------------------------------

Thanks Jonathan,
but why do we need them alive? 
for example

I create a 2MB region, which is carved out to 100 ByteBuffers, each of these ByteBuffers would
point to the "data" of the Region, so as long as one of them is live, the bytes pointed to
by Region.data is still in heap; and if these 100 ByteBuffers all die, isn't it our goal to
free the 2MB region, since no one is using them??




> arena allocation for memtables
> ------------------------------
>
>                 Key: CASSANDRA-2252
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2252
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 1.0
>
>         Attachments: 0001-add-MemtableAllocator.txt, 0002-add-off-heap-MemtableAllocator-support.txt,
2252-v3.txt, 2252-v4.txt, merged-2252.tgz
>
>
> The memtable design practically actively fights Java's GC design.  Todd Lipcon gave a
good explanation over on HBASE-3455.

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