Marcel Reutegger created OAK-591:
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Summary: 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
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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