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Posted to dev@directmemory.apache.org by "Raffaele P. Guidi (Commented) (JIRA)" <ji...@apache.org> on 2012/02/19 10:14:34 UTC
[jira] [Commented] (DIRECTMEMORY-63) Investigate removing the need
for an on heap map to store keys/pointers.
[ https://issues.apache.org/jira/browse/DIRECTMEMORY-63?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13211291#comment-13211291 ]
Raffaele P. Guidi commented on DIRECTMEMORY-63:
-----------------------------------------------
Well, the general idea was, from the beginning, to keep "indexes" into the heap and data outside the heap; I've made attempts at keeping the "index" part (pointers and keys) as thin as possible and come up with Guava collections as the better tradeoff. I also tried using CRC32 instead of keys but didn't work out well (too hard to calculate). I meant to give Vanilla HugeCollections (http://code.google.com/p/vanilla-java/wiki/HugeCollections - off-heap collections of homogeneus objects) a try to make the Pointer's part even lighter but still havent' had a chance to play with it (do someone knows the thing?). Of course the most heavyweight part is now the key itself and maybe it's worth a bit of hacking
> Investigate removing the need for an on heap map to store keys/pointers.
> ------------------------------------------------------------------------
>
> Key: DIRECTMEMORY-63
> URL: https://issues.apache.org/jira/browse/DIRECTMEMORY-63
> Project: Apache DirectMemory
> Issue Type: Improvement
> Reporter: Michael André Pearce
>
> On performance testing and monitoring jvm heap allocation, it became clear that as the off heap elements increased so did the on heap used memory. This is because DirectMemory is storing keys and pointers in the heap meaning that the cache isn't fully off heap, and on heap memory will increase linearly with elements in the cache.
> An idea maybe is to look into using a key's hash for location on a separate single off heap buffer to store the main heaps pointers.
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