Can the caching mechanism be improved?
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Key: JCR-731
URL: https://issues.apache.org/jira/browse/JCR-731
Project: Jackrabbit
Issue Type: Improvement
Reporter: Martijn Hendriks
Hi all,
We've identified the method "getNonVirtualItemState" in the
SharedItemStateManager as a hot spot in our application. To avoid the
contention in "getNonVirtualItemState", we have pulled the isCached call out of
the synchronized block and re-implemented the MLRUItemStateCache. It uses a
HashMap that contains the ItemId-ItemState mapping and a ReadWriteLock to
replace all synchronized blocks in the code. The implementation of
"shrinkIfRequired" unfortunatly got much more expensive as the entryset of the
HashMap must be sorted by accesscount. This method then clearly is a
bottleneck. We solved this by changing the CacheManager a bit: the "resizeAll"
method avoids the eviction of items out of caches as long as possible.
These changes work out really well for our application. I have attached the
changed files; comments/feedback are very welcome!
Regards,
Martijn Hendriks
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