[jira] [Commented] (OAK-891) Use DirectMemory as Level 2/Offheap cache

["Michael Marth (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13843059#comment-13843059 ] 

Michael Marth commented on OAK-891:
-----------------------------------

[~chetanm], are we good to start testing?

> Use DirectMemory as Level 2/Offheap cache
> -----------------------------------------
>
>                 Key: OAK-891
>                 URL: https://issues.apache.org/jira/browse/OAK-891
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 0.8
>            Reporter: Chetan Mehrotra
>            Assignee: Chetan Mehrotra
>         Attachments: OAK-891-1.patch
>
>
> To make optimum use of memory allocated to the various caches created in Oak it would be better to use Apache DirectMemory [1] as the level 2 (L2) cache. Further using Kryo[2] Serializer would enable saving of serialized objects in more compact form
> * Storing cache objects in serialized form provides a more compact storage
> * Deserializtion cost is low
> * Using Off heap memory would be helpful compared to on heap memory
> * L2 cache can be added as an optional feature. Oak Core can still be
> used in absence of L2 cache
> Implementation details 
> * [Feature Branch|https://github.com/chetanmeh/jackrabbit-oak/tree/offheap]
> * [Diff |https://github.com/chetanmeh/jackrabbit-oak/compare/apache:ab955ffd40e23a9f8aee87f9076bc045b643e35d...offheap]
> * Test cases to be added
> Implementation notes
> * Adds DirectMemory and Kryo library as optional dependencies
> * Decorates the Guava Cache to move the evicted objects to L2 cache
> * Using L2 cache is completely optional
> * Kryo library is used to provide fast and compact serialization. 
> * Uses custom serializers for various cache instances to provide a more compact storage
> * Instead of using the key as is (i.e. path in MongoMK) it stores the hash of the path to conserve memory
> Initial discussion at http://markmail.org/thread/xief4l25m7tnx52c
> [1] http://directmemory.apache.org/
> [2] https://code.google.com/p/kryo/



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