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Posted to oak-issues@jackrabbit.apache.org by "Mete Atamel (JIRA)" <ji...@apache.org> on 2013/01/29 16:13:14 UTC
[jira] [Commented] (OAK-591) Improve KernelNodeStore cache
efficiency
[ https://issues.apache.org/jira/browse/OAK-591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13565442#comment-13565442 ]
Mete Atamel commented on OAK-591:
---------------------------------
Is this a more general problem about the MicroKernel API rather than just KernelNodeStore? In MongoMK, a similar problem exists. Instead of caching a node under path, MongoMK caches it under path + revision id because a node can be retrieved by path and revision id according to MicroKernel API (rather than just path). Is this another manifestation of the same problem?
> Improve KernelNodeStore cache efficiency
> ----------------------------------------
>
> Key: OAK-591
> URL: https://issues.apache.org/jira/browse/OAK-591
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core
> Affects Versions: 0.6
> Reporter: Marcel Reutegger
> Attachments: mk.log.gz, OAK-591.patch
>
>
> The cache in KernelNodeStore references entries with a path+revision combo. This mapping quickly becomes inefficient when there are writes on the repository. Whenever something is changed, the complete cache basically becomes invalid and oak-core needs to re-fetch nodes again, even though they didn't change. The attached test shows this behaviour. The test initially creates 10 nodes and lets a thread read those nodes repeatedly. To make the test somewhat realistic the reader acquires a new session in every run through the loop. This is to simulate e.g. a request which acquires a new session every time (Apache Sling does it that way). At the same time writes occur but in a separate part of the repository. As can be seen in the logs, the nodes are read from the MicroKernel whenever something changes anywhere in the repository. Obviously this is no limited to the test nodes. The log also shows repeated reads to node type, user and index nodes. None of them change while the test runs.
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