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https://issues.apache.org/jira/browse/DIRECTMEMORY-9?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13176606#comment-13176606
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Raffaele P. Guidi commented on DIRECTMEMORY-9:
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Mmm... a nifty trick! I really like the idea
> Add a defragmentation mechanism
> -------------------------------
>
> Key: DIRECTMEMORY-9
> URL: https://issues.apache.org/jira/browse/DIRECTMEMORY-9
> Project: Apache DirectMemory
> Issue Type: Task
> Reporter: Raffaele P. Guidi
> Labels: defrag,, defragmentation
>
> Add a defragmentation mechanism
> From the ML: (paliwalashish)
> >Will the offHeapMemoryBuffer get fragmented over time? Say after a
> couple thousand get/remove operations, will the off-heap have start
> having holes in the Buffer?
> (Me:)
> >It will, definitely. I had two solutions ready in my mind (that rely on
> >having more than one buffer active):
> Simplest, and fastest but with some drawbacks: when
> buffer.isTooDefragmented() then simply buffer.clear() - you loose everything,
> but - hey, it's a cache, not a db
> Less simple, slower, less drawbacks: when buffer.isTooDefragmented() mark the
> buffer as readOnly and then foreach (ptr in buffer) copy ptr.content in
> emptyBuffer and update ptr accordingly
> where isTooFragmented==number_of_empty_pointers over total_pointers >
> desirable quota
> The first one could be accomplished during a put() operation (buffer.clear is
> a logical operation that takes no time) while the second should be taken care
> of by the background thread. Those quick&dirty solutions could of course be
> replaced with real defragmentation algorithms - may taken from various
> malloc() implementations, that are the original inspiration
> http://en.wikipedia.org/wiki/Malloc#Implementations
> See also https://github.com/raffaeleguidi/DirectMemory/issues/43
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