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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Commented] (OAK-4635) Improve cache eviction policy of the node deduplication cache
Date Wed, 03 Aug 2016 13:40:20 GMT

    [ https://issues.apache.org/jira/browse/OAK-4635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15405927#comment-15405927
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Michael Dürig commented on OAK-4635:
------------------------------------

At https://github.com/mduerig/jackrabbit-oak/commit/962e7a76ae92e6662d46b69a23766b0e792e06e1
I implemented another alternative where stripes are organised by cost instead of depth. The
cost is currently equal to the number of child nodes of a node unless the node has depth 4
or smaller. In this case its cost is maximal to avoid checkpoints being evicted from the cache.


> Improve cache eviction policy of the node deduplication cache
> -------------------------------------------------------------
>
>                 Key: OAK-4635
>                 URL: https://issues.apache.org/jira/browse/OAK-4635
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segment-tar
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig
>              Labels: perfomance
>             Fix For: Segment Tar 1.0.0
>
>
> {{NodeCache}} uses one stripe per depth (of the nodes in the tree). Once its overall
capacity (default 1000000 nodes) is exceeded, it clears all nodes from the stripe with the
greatest depth. This can be problematic when the stripe with the greatest depth contains most
of the nodes as clearing it would result in an almost empty cache. 



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