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Posted to dev@bookkeeper.apache.org by "Ivan Kelly (JIRA)" <ji...@apache.org> on 2013/03/04 19:35:13 UTC

[jira] [Commented] (BOOKKEEPER-578) LedgerCacheImpl is reserving 1/3 of Heap size but allocates NonHeap memory

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13592462#comment-13592462 ] 

Ivan Kelly commented on BOOKKEEPER-578:
---------------------------------------

As I understand it, direct byte buffers can be used for DMA, which skips a memory copy when reading in pages.
                
> LedgerCacheImpl is reserving 1/3 of Heap size but allocates NonHeap memory
> --------------------------------------------------------------------------
>
>                 Key: BOOKKEEPER-578
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-578
>             Project: Bookkeeper
>          Issue Type: Bug
>          Components: bookkeeper-server
>            Reporter: Matteo Merli
>            Priority: Minor
>
> By default the page limit parameter is set to -1, which means to assign 1/3 of Heap space to the LedgerCache. Each LedgerEntryPage is then allocating the memory outside the heap (ByteBuffer.allocateDirect()).
> This makes BK to use more memory than the -XmxNN configured setting. Is there any particular reason for the LedgerEntryPage buffer to be allocated outside the java heap? Could that be changed?

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