Thilo Goetz (JIRA) wrote:
Some applications may break if they require == between instances of the
same JCas object. Other of course won't care. So - it's good for this
to be configurable.
It might be good, also, to put in "soft references" for this - which
will be reclaimed if memory gets low. But this might end up doubling
the size of the storage used for this (to hold the soft reference)...
-Marshall
Use of the JCas cache should be configurable
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Key: UIMA-1068
URL: https://issues.apache.org/jira/browse/UIMA-1068
Project: UIMA
Issue Type: Improvement
Components: Core Java Framework
Affects Versions: 2.2.2
Reporter: Thilo Goetz
Assignee: Thilo Goetz
Fix For: 2.3
The JCas caches all CAS objects that are accessed through it. This means that
JCas objects that are no longer used can't be garbage collected. If only part
of the processing chain uses the JCas, or the caching is redundant for some
other reason, this produces a severe memory overhead.
I ran the same experiment I ran for UIMA-1067: doubled the size of Moby Dick
and ran the POS tagger from the sandbox. I used the improved version from
UIMA-1067 as base case and simply commented out the line that adds JCas objects
to the cache. This reduced the required heap size from 115MB to 105MB. It
also improved the performance from around 10s for the base case to consistently
under 9s for the version without any caching. I looked at the tagger source
code, and saw that it keeps its own list of tokens around. So the savings are
just the caching data structure.
There may be cases where the JCas cache is a performance win, though I'd be
curious to see the benchmarks. So we should not just turn it off, but make it
configurable.
