Jan De Beer created JENA-902:
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Summary: Default cache sizes too large / configurability should be
more exposed
Key: JENA-902
URL: https://issues.apache.org/jira/browse/JENA-902
Project: Apache Jena
Issue Type: Improvement
Components: TDB
Affects Versions: TDB 1.1.0
Reporter: Jan De Beer
In the class "com.hp.hpl.jena.tdb.sys.SystemTDB" there are two important cache
size settings, namely "Node2NodeIdCacheSize" and "NodeId2NodeCacheSize". On a
64-bit platform, they default to 100000 and 500000 entries.
In our setup of 5 TDB-backed graphs inside a single dataset, these default
settings led to out-of-memory errors of the Fuseki server although setting the
available heap memory to 3GB. It took some heap analysis to reveal that these
two caches were the main memory consumers. Also, from the public documentation
of Fuseki / TDB, it wasn't so obvious that their sizes can be configured. Only
by looking into the source code, we found that one can use a TDB properties
file to override the defaults.
Proposed is to lower the default settings and have a more exposed documentation
as to tuning the memory settings of TDB.
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